© 2014 American Society of Plant Biologists
Potassium: Potash, from the ashes
in the pot
Regulates
stomatal
conductance,
photosynthesis
and transpiration
Maintains turgor
and reduces wilting
Strengthens
cell walls Maintains ionic
balance Stimulates
photosynthate
translocation
Enhances
fertility
Promotes stress
tolerance
See Wang, M., Zheng, Q., Shen, Q. and Guo, S. (2013). The critical role of potassium in plant stress response. Intl. J. Mol. Sci. 14: 7370-7390; Sin Chee Tham /Photo; Purdue extension; Onsemeliot.
Symptoms of
potassium deficiency
[K+] in soil = ~0.1 – 1 mM
[K+] in plant cell
cytoplasm = ~100 mM
Potassium is an essential macronutrient
Regulates
enzyme activities
© 2014 American Society of Plant Biologists
Potassium fertilizers are mined from
underground reserves as “potash”
Almost half of the world’s reserved of potash
are found in Saskatchewan, Canada
Potash is a term that encompasses
many forms of potassium:
• KCl (potassium chloride, aka sylvite)
• K2SO4 (potassium sulfate)
• K2CO3 (potassium carbonate)
• K2Ca2Mg(SO4)4·2H2O (polyhalite)
• etc.
Canada Potash; Lmbuga
KCl, sylvite
For historical reasons, potash
is measured in units of K2O
equivalents, even though it is
rarely found in the form of K2O
© 2014 American Society of Plant Biologists
Potash provides K for fertilizers,
which supplement natural sources
manure
decomposition
Terrestrial
cycle: Plant /
Animal / Soil Underground reserves
Water with
dissolved K+
salts returned
to surface
Water
pumped
underground
Salts
recovered by
evaporation
90 – 98%
insoluble
minerals
1 – 3%
exchangeable
salts
0.1 – 0.2% soil
solution K+
Potash
fertilizer
application
Adapted from International Potash Institute
© 2014 American Society of Plant Biologists
Potash prices can be volatile and
there are few suppliers
1.06 cm
Canada is #1
in production
(11.2 Mt) and
reserves
(4,400 Mt)
Russia is #2
in production
(7.4 Mt) and
reserves
(3,300 Mt)
Brazil
3.2 Mt
210 Mt
Chile
0.8 Mt
130 Mt
US
1.1 Mt
130 Mt
China
3.2 Mt
210 Mt
Belarus
5.5 Mt
750 Mt
World
reserves
9500 Mt
World
production
(2011)
37 Mt
Jordan
1.4 Mt
40 Mt
Israel
2.0 Mt
40 Mt
Germany
3.3 Mt
150 Mt
Spain
0.4 Mt
20 Mt
UK
0.4 Mt
22 Mt
Adapted from International Potash Institute
© 2014 American Society of Plant Biologists
Potassium is an essential plant
nutrient
Reprinted from Maathuis, F.J.M. (2009). Physiological functions of mineral macronutrients. Curr. Opin. Plant Biol. 12: 250-258 with permission from Elsevier.
K+ uptake
involves high
and low affinity
transporters
K+ is a counter ion for
negatively charged molecules
including DNA and proteins
K+ is a cofactor for
some enzymes
As the major cation in
the vacuole, K+
contributes to cell
expansion and
movement, including
that of guard cells
K+ moves in and
out of the vacuole
through specific
transporters
© 2014 American Society of Plant Biologists
Early studies of potassium uptake in
plants: Biphasic uptake
Epstein, E., Rains, D.W., and Elzam, O.E. (1963). Resolution of dual mechanisms of potassium absorption by barley roots. Proc. Natl. Acad. Sci. USA. 49: 684 – 692;
Gierth, M. and Mäser, P. (2007). Potassium transporters in plants – Involvement in K+ acquisition, redistribution and homeostasis. FEBS Lett. 581: 2348-2356.
KCl (mM)
Low affinity
transport
High affinity
transport
Epstein et al showed
two phases of K+
uptake in barley roots
K+ K+ H+
H+
ATP
2 x H+
2 x ATP
Low affinity
transport
High affinity
transport
K+ uptake from low [K+]ext
requires more energy than
when [K+]ext is higher
Co-transporter
mediated
Channel
mediated
© 2014 American Society of Plant Biologists
K+ mobilization is critical for K+ use
efficiency
Adapted from Amtmann, A., and Leigh, R. (2010). Ion homeostasis. In Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic
Foundation, A. Pareek, S.K. Sopory, H.J. Bohnert and Govindjee (eds) (Dordrecht, The Netherlands: Springer), pp. 245 – 262.
Cytosol
Vac.
Supraoptimal K+
can be stored in
the vacuole As K+ becomes
limiting, it becomes
preferentially allocated
to the cytosol
© 2014 American Society of Plant Biologists
K+ mobilization is critical for K+ use
efficiency
Cytosol
Vac.
Prioritized
Non-
Prioritized
As K+ becomes
limiting, it becomes
preferentially allocated
to the cytosol
K+ can be remobilized
from less essential tissues
into prioritized tissues
such as growing and
photosynthetic tissues
Adapted from Amtmann, A., and Leigh, R. (2010). Ion homeostasis. In Abiotic Stress Adaptation in Plants: Physiological, Molecular and Genomic
Foundation, A. Pareek, S.K. Sopory, H.J. Bohnert and Govindjee (eds) (Dordrecht, The Netherlands: Springer), pp. 245 – 262.
© 2014 American Society of Plant Biologists
Summary: Potassium uptake,
transport and regulation
• Potassium is an essential macronutrient required
in large amounts
• Potassium uptake involves low and high affinity
transporters
• K+ uptake, transport and remobilization are
regulated extensively to ensure that the plant’s
critical tissues are preferentially supported
© 2014 American Society of Plant Biologists
Sulfur: Clean air can lead to
deficient plants
International Society of Arboriculture; Robert L. Anderson, USDA Forest Service; D'Hooghe, P., Escamez, S., Trouverie, J. and Avice, J.-C. (2013). Sulphur limitation provokes physiological and leaf proteome changes
in oilseed rape that lead to perturbation of sulphur, carbon and oxidative metabolisms. BMC Plant Biol. 13: 23. Hay and Forage.
Sulfur
dioxide
damage
Until recently, sulfur dioxide emission from
fossil fuel combustion led to acid rain and
extensive damage to vulnerable plants
Eliminating S from air
pollution uncovered
crop plant
deficiencies,
particularly in oilseed
rape and wheat
© 2014 American Society of Plant Biologists
Sulfur can be found in many
inorganic forms Species Name Oxidation
State
S2-, H2S, R-SH Sulfide -2
S0, S8 Sulfur 0
SO2 Sulfur dioxide (toxic gas) +4
SO3- Sulfite +4
SO42- Sulfate +6
Plants take up sulfur from soil as SO42- and to a
lesser extent from the atmosphere as SO2 or H2S
Organic S
R-SH
SO42-
S0
H2S
Sulfur
deposits
SO3-
© 2014 American Society of Plant Biologists
Plants are an important part of the
global sulfur cycle Atmospheric pool of sulfur – mostly SO2 (sulfur dioxide)
Combustion
of fossil fuels
Prokaryotic oxidation
R-SH
manure
Assimilation
by plants decomposition
SO2 SO42- H2O
O2
SO42- S
Volcanic activity
SO42-
Acid
rain*
*Since the 1980s,
SO2 emissions and
SO42- precipitation
have been declining
H2S
Prokaryotic reduction
See for example Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic
organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.
© 2014 American Society of Plant Biologists
Sulfur is an essential macronutrient
in amino acids & other compounds
HS-CH2-CH-COOH
NH2
H3C-S-CH2-CH2-CH-COOH
NH2
Methionine (Met)
Cysteine (Cys)
Amino
acids
Cys Glutathione Glutathione is an amino
acid derivative involved
in Redox reactions
Oxidation /reduction,
metal transport and
detox
S
Allicin (garlic flavor)
Allyl-isothiocyanate
(horseradish flavor)
Flavor or
odor
SH
O
Mercapto-p-
menthan-3-one
(blackcurrant)
S S
S S
Defense Glucosinolates are
anti-herbivores
Camalexin is a
defense compound
induced by pathogens
S
S
McGorrin, R.J. (2011). The significance of volatile sulfur compounds in food flavors. Volatile Sulfur Compounds in Food. ACS Symposium Series, Vol. 1068: 3-31
© 2014 American Society of Plant Biologists
Sulfate uptake occurs primarily
through SULTR transporters
Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773 with permission from Oxford University Press; Smith, F.W., Ealing,
P.M., Hawkesford, M.J. and Clarkson, D.T. (1995). Plant members of a family of sulfate transporters reveal functional subtypes. Proc. Natl. Acad. Sci. USA 92: 9373-9377. Rouached, H., Secco, D. and Arpat, A.B. (2009). Getting the most sulfate from
soil: Regulation of sulfate uptake transporters in Arabidopsis. J. Plant Physiol. 166: 893-902. Gojon, A., Nacry, P. and Davidian, J.-C. (2009). Root uptake regulation: a central process for NPS homeostasis in plants. Curr. Opin. Plant Biol. 12: 328-338.
In Arabidopsis, 12 genes
encode SULTR transporters that
fall into four groups
Most are 12-membrane spanning
SO42- / H+ co-transporters
SO42- H+
SO42- H+
Primary assimilation in roots occurs mainly
through SULTR1;1 and SULTR1;2
© 2014 American Society of Plant Biologists
In higher plants, SULTR transporters
effect inter-organelle movement
Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773; Gigolashvili, T. and Kopriva, S. (2014).
Transporters in plant sulfur metabolism. Frontiers in Plant Science. 5: 442. Rennenberg, H. and Herschbach, C. (2014). A detailed view on sulphur metabolism at the cellular and whole-plant level illustrates challenges in
metabolite flux analyses. J. Exp. Bot. 65 : 5711-5724.
Vacuole
Plastid
Cytosol
[SO42-] 6 – 75 mM
[SO42-] ≤ 10 μM
[SO42-] 1 – 11 mM
[SO42-]
4 – 12 mM
SO42- H+
SULTR
SO42-
H+
SULTR
SO42-
H+
STORAGE
SULTR
SO42-
S2-
Sulfate
reduction only
occurs in
plastids
© 2014 American Society of Plant Biologists
Buchner, P., Takahashi, H. and Hawkesford, M.J. (2004). Plant sulphate transporters: co-ordination of uptake, intracellular and long-distance transport. J. Exp. Bot. 55: 1765-1773 by permission of Oxford University Press.
S transporters
coordinate
long-distance
transport too
© 2014 American Society of Plant Biologists
Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.
Uptake
Adenosine 5'-phosphosulfate
5'-Phosphoadenosine
3'-phosphosulfate
Primary sulfur
metabolism (overview)
© 2014 American Society of Plant Biologists
Sulfate is assimilated by ATP
sulfurylase into APS
Sulfate ATP
+
Pyrophosphate
(PPi) Adenosine 5'-
phosphosulfate (APS)
+
ATP
sulfurylase
Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic
organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.
This reaction occurs in the
cytosol and plastid
© 2014 American Society of Plant Biologists
APS can enter two pathways for
primary or secondary reactions
Adenosine 5'-
phosphosulfate (APS)
APS
kinase
ATP
ADP
5'-Phosphoadenosine 3'-
phosphosulfate (PAPS)
Sulfated compounds,
glucosinolates
APS
reductase
Sulfite
reductase Sulfite
Sulfide
AMP
SO32- S2-
2 GSH
GSSG FdxRed
FdxOx
Cysteine
Located exclusively in plastids
Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic
organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu. Rev. Plant Biol. 62: 157-184.
© 2014 American Society of Plant Biologists
Sulfide is assimilated into cysteine
by the cysteine synthase complex
Reprinted from Jez, J.M. and Dey, S. (2013). The cysteine regulatory complex from plants and microbes: what was old is new again. Curr. Opin. Structural Biol. 23: 302-310 with permission from Elsevier.
O-acetylserine (OAS)
indicates cellular S
status: when S is low,
OAS accumulates
Adenosine 5'-
phosphosulfate (APS)
(thiol)lyase (OAS-TL)
Cysteine
synthase is a
complex of SAT
and OAS-TL,
and is present
in the cytosol,
plastid and
mitochondria
© 2014 American Society of Plant Biologists
Model for regulation of cysteine
synthesis by the CS complex
Reprinted from Jez, J.M. and Dey, S. (2013). The cysteine regulatory complex from plants and microbes: what was old is new again. Curr. Opin. Structural Biol. 23: 302-310 with permission from
Elsevier.Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.
When SO42- is available,
free OAS-TL dimers
produce cysteine
OAS is synthesized by SAT within
the cysteine synthase (CS) complex
SAT CS OAS-TL is inactive
within the CS complex
© 2014 American Society of Plant Biologists
Model for regulation of cysteine
synthesis by the CS complex
Hell, R. and Markus Wirtz, M. (2011). Molecular Biology, Biochemistry and Cellular Physiology of Cysteine Metabolism in Arabidopsis thaliana. The Arabidopsis Book 9: e0154.
When SO42- is
unavailable, OAS
accumulates, causing the
CS complex to dissociate,
and decreasing the
activity of SAT. Thus, the
rate of production of OAS
decreases
Free SAT is deactivated
© 2014 American Society of Plant Biologists
Sulfur uptake and assimilation rates
are metabolically regulated
Adapted from Takahashi, H., Kopriva, S., Giordano, M., Saito, K. and Hell, R. (2011). Sulfur assimilation in photosynthetic organisms: Molecular functions and regulations of transporters and assimilatory enzymes. Annu.
Rev. Plant Biol. 62: 157-184; Davidian, J.-C. and Kopriva, S. (2010). Regulation of sulfate uptake and assimilation—the same or not the same? Mol. Plant. 3: 314-325. Yi, H., Galant, A., Ravilious, G.E., Preuss, M.L. and
Jez, J.M. (2010). Sensing sulfur conditions: Simple to complex protein regulatory mechanisms in plant thiol metabolism. Mol. Plant. 3: 269-279.
SO42-
out
SO42-
in
SULTR
APS
Reductase
Cys Synthase
SO3-
Cys
Transcriptional, post-
transcriptional and post-
translational / allosteric
regulation of transporters
Local sulfate levels
OAS
OAS
Allosteric interactions,
metabolic regulation
Reduced sulfur
(glutathione, Cys etc)
Light, carbon and
nitrogen reserves,
circadian rhythms etc)
Transcriptional regulation
of ATP sulfurylase and
adenosine 5'-
phosphosulfate (APS)
reductase (APR)
ATP
Sulfurylase
© 2014 American Society of Plant Biologists
SLIM (EIL3) coordinates many
transcriptional responses to S
Maruyama-Nakashita, A., Nakamura, Y., Tohge, T., Saito, K. and Takahashi, H. (2006). Arabidopsis SLIM1 is a central transcriptional regulator of plant sulfur response and metabolism. Plant Cell. 18: 3235-3251.
SLIM = Sulfur
Limitation
Red, pink =
up-regulated by
S-deficiency
Blue =
down-regulated
by S-deficiency
Thioglucosidase activity
(increased by S-
deficiency) liberates S
for recycling
© 2014 American Society of Plant Biologists
Addressing S deficiency in plants
D'Hooghe, P., Escamez, S., Trouverie, J. and Avice, J.-C. (2013). Sulphur limitation provokes physiological and leaf proteome changes in
oilseed rape that lead to perturbation of sulphur, carbon and oxidative metabolisms. BMC Plant Biol. 13: 23. Hay and Forage.
S sufficient S deficient With stricter laws
on S emissions,
less S enters
soils and plants
are more prone
to S deficiency
Soil can be
augmented with
elemental sulfur,
ammonium sulfate or
other fertilizers
© 2014 American Society of Plant Biologists
Summary: Sulfur uptake and
metabolism
• Found in many redox forms and can be assimilated from
atmosphere
• Deficiency more common with cleaner air
• SULTR transporter family primarily involved in uptake
and transport
• Uptake and assimilation into organic forms subject to
positive and negative regulation
© 2014 American Society of Plant Biologists
Magnesium: The “forgotten
element”
Didier Descouens; Ra’ike; chensiyuan; James St. John
Mg in solution is a
divalent cation Mg2+
Soil magnesium is a
result of rock
weathering and Mg2+
from seawater
Serpentine
3MgO*2SiO2*2H2O
The Dolomite Mountains are
named for the mineral dolomite
MgCO3*CaCO3
Magnesite
MgCO3
© 2014 American Society of Plant Biologists
Magnesium is a cofactor for many
enzymes and central to chlorophyll Mg2+ is a counter
ion for the negative
charges of ATP
Mg2+
stabilizes
ribosome
3D structure
Mg2+ is central
to chlorophyll
Mg2+ is an essential
activator for many
enzymes including
Rubisco
Jensen, R.G. (2000). Activation of Rubisco regulates photosynthesis at high
temperature and CO2. Proc. Natl. Acad. Sci. USA 97: 12937-12938.
© 2014 American Society of Plant Biologists
Mg deficiency interferes with
photosynthesis & C transport
Reused with permission from Wiley from Cakmak, I. and Kirkby, E.A. (2008). Role of magnesium in carbon partitioning and alleviating photooxidative damage. Physiol. Plant.
133: 692-704; See also Verbruggen, N., and Hermans, C. (2013). Physiological and molecular responses to magnesium nutritional imbalance in plants. Plant Soil. 368: 87 – 99.
Effects of Mg deficiency
One symptom of Mg
deficiency is high-light
induced chlorosis
© 2014 American Society of Plant Biologists
Magnesium transporters move Mg2+
across membranes
Reproduced from Hermans, C., Conn, S.J., Chen, J., Xiao, Q. and Verbruggen, N. (2013). An update on magnesium homeostasis mechanisms in plants. Metallomics. 5: 1170-1183 with permission of The Royal Society
of Chemistry; Reprinted by permission from Macmillan Publishers Ltd Hattori, M., Tanaka, Y., Fukai, S., Ishitani, R. and Nureki, O. (2007). Crystal structure of the MgtE Mg2+ transporter. Nature. 448: 1072-1075.
There are two known
classes of Mg transporters:
MRS/MGT
MHX (Mg/H+ exchanger)
Proposed structure and
mechanism of an MRS-type
transporter
Mg transporters are
different from other cation
transporters but conserved
across life domains
© 2014 American Society of Plant Biologists
Magnesium uptake is mediated by
the MRS / MGT family
Gebert, M., Meschenmoser, K., Svidová, S., Weghuber, J., Schweyen, R., Eifler, K., Lenz, H., Weyand, K. and Knoop, V. (2009). A root-expressed magnesium transporter of the MRS2/MGT gene family in Arabidopsis
thaliana allows for growth in low-Mg2+ environments. Plant Cell. 21: 4018-4030. Mao, D., Chen, J., Tian, L., Liu, Z., Yang, L., Tang, R., Li, J., Lu, C., Yang, Y., Shi, J., Chen, L., Li, D. and Luan, S. (2014). Arabidopsis
transporter MGT6 mediates magnesium uptake and is required for growth under magnesium limitation. Plant Cell. 26: 2234-2248.
MGT6 RNAi WT
MGT6 is induced in roots
by low Mg and required
for efficient Mg uptake
© 2014 American Society of Plant Biologists
Aluminum toxicity is minimized by
increased Mg uptake
Delhaize, E., and Ryan, P.R. (1995). Aluminum toxicity and tolerance in plants. Plant Physiol. 107: 315 – 321. Bose, J., Babourina, O. and Rengel, Z.
(2011). Role of magnesium in alleviation of aluminium toxicity in plants. J. Exp. Bot. 62: 2251-2264, by permission of Oxford University Press.
Al tolerant
Al sensitive
Al inhibits growth,
especially in low pH soils
where it is most soluble
Elevated Mg soil
levels or uptake
can minimize Al
toxicity mainly
through
competition for
uptake and
molecular
interactions
© 2014 American Society of Plant Biologists
Mg deficiency in plants contributes
to Mg deficiency in animals
Peggy Greb USDA
Rapidly growing spring grass can be low
in Mg, so grass-fed cattle can experience
hypomagnesemia, a sometimes fatal
condition called grass tetany
Mg2+
To ensure adequate dietary
Mg2+, human diets should
include nuts, legumes,
leaves and whole grains
© 2014 American Society of Plant Biologists
Summary: Magnesium
• Rarely limiting for plant growth
• Mg2+ transporters are different from other cation
transporters, but conserved across life domains
• Elevated Mg2+ uptake can mitigate Al3+ toxicity
• Humans and animals can suffer Mg deficiency if dietary
sources are deficient
© 2014 American Society of Plant Biologists
Calcium: Low free cytosolic levels &
functions in apoplast / vacuole
Capoen, W., Den Herder, J., Sun, J., Verplancke, C., De Keyser, A., De Rycke, R., Goormachtig, S., Oldroyd, G. and Holsters, M. (2009). Calcium spiking patterns and the role of the calcium/calmodulin-dependent
kinase CCaMK in lateral root base nodulation of Sesbania rostrata. Plant Cell. 21: 1526-1540. Bose, J., Pottosin, I., Shabala, S.S., Palmgren, M.G. and Shabala, S. (2011). Calcium efflux systems in stress signalling and
adaptation in plants. Front. Plant Sci. 2: 85. Persson, S., Caffall, K.H., Freshour, G., Hilley, M.T., Bauer, S., Poindexter, P., Hahn, M.G., Mohnen, D. and Somerville, C. (2007). The Arabidopsis irregular xylem8 mutant
is deficient in glucuronoxylan and homogalacturonan, which are essential for secondary cell wall integrity. Plant Cell. 19: 237-255.
Middle lamella
Primary wall Secondary
wall
2 μm
Calcium
stabilizes pectin
in middle lamella
of cell walls
Cytosolic Ca2+
oscillations are
second
messengers in
diverse responses
© 2014 American Society of Plant Biologists
90% of the plant’s calcium can be in
the form of calcium oxalate crystals
Webb, M.A. (1999). Cell-mediated crystallization of calcium oxalate in plants. Plant Cell. 11: 751-761; Franceschi, V.R. and Nakata, P.A. (2005). Calcium oxalate in
plants: Formation and Function. Annu. Rev. Plant Biol. 56: 41-71. Kostman, T.A., Tarlyn, N.M., Loewus, F.A. and Franceschi, V.R. (2001). Biosynthesis of l-ascorbic
acid and conversion of carbons 1 and 2 of l-ascorbic acid to oxalic acid occurs within individual calcium oxalate crystal idioblasts. Plant Physiol. 125: 634-640.
Idioblasts are specialized
cells that form calcium
oxalate crystals and are
illuminated by polarized light (RI = raphide idioblast
DI = druse idioplast)
• The crystals are
formed by
specialized cells
called idioblasts
• Calcium oxalate
crystals can function
in defense
• Calcium oxalate
crystals also can
sequester excess
calcium
Prismatic
crystals from
bean seed coat
Druse crystals
from velvet leaf
(Abutilon
theophrasti)
Bundle of
raphide crystals
from grape leaf
© 2014 American Society of Plant Biologists
Plants maintain very low levels of
free cytosolic Ca2+
Stael, S., Wurzinger, B., Mair, A., Mehlmer, N., Vothknecht, U.C. and Teige, M. (2012). Plant organellar calcium signalling: an emerging field. J. Exp. Bot. 63: 1525-1542 by permission of Oxford University Press .
The concentration of
free Ca2+ is ~ 10,000
fold lower in the
cytosol than the
apoplast
The challenge at the
plasma membrane is
to maintain low free
internal Ca2+ (in
contrast to the situation
for most other
nutrients)
© 2014 American Society of Plant Biologists
Ca2+ transport systems include
channels, pumps and antiporters
Kudla, J., Batistič, O. and Hashimoto, K. (2010). Calcium signals: The lead currency of plant information processing. Plant Cell. 22: 541-563.
© 2014 American Society of Plant Biologists
Calcium deficiency causes cell wall
defects and sometimes cell death
White, P.J. and Broadley, M.R. (2003). Calcium in plants. Ann. Bot. 92: 487-511. Maine.gov; David B. Langston, University of Georgia; University of Georgia Plant Pathology Archive Bugwood.org
Ca2+
Calcium is
translocated in the
xylem (apoplast)
but not the phloem
(symplast),
meaning that it
cannot be
remobilized when
external supplies
are limited
Ca2+ deficiency in growing tissues causes
weakness and death, leading to blossom
end rot (left), tip burn (right) and bitter pit
(bottom). Ca2+ deficiency also can result
from a low rate of transpiration.
© 2014 American Society of Plant Biologists
Calcium contributes to pectin
crosslinking and stabilization
Sundar Raj AA, Rubila S, Jayabalan R, Ranganathan TV (2012) A review on pectin: Chemistry due to general properties of pectin and its pharmaceutical uses. 1:550 doi:10.4172/scientificreports.550 (adapted from
Axelos and Thibault, 1991). Hepler, P.K. and Winship, L.J. (2010). Calcium at the cell wall-cytoplast interface. J. Integr. Plant Biol. 52: 147-160, with permission from Wiley.
Pectin is found in the middle
lamella and the cell wall of a
growing pollen tube
Middle lamella
Pectin is a
galacturonic acid
polymer. Calcium
stabilizes the pectin
and causes it to “gel”
Ca2+ interacting
with pectin at tip
of pollen tube
Molecular gastronomists react
calcium with pectin-like polymers
to produce interesting foods
Ca2+
Pectin
© 2014 American Society of Plant Biologists
Calcium oscillations are mediated by
ion channels, pumps and carriers
Venkateshwaran, M., Cosme, A., Han, L., Banba, M., Satyshur, K.A., Schleiff, E., Parniske, M., Imaizumi-Anraku, H. and Ané, J.-M. (2012). The recent evolution of a symbiotic ion channel in the legume family altered
ion conductance and improved functionality in calcium signaling. Plant Cell. 24: 2528-2545. Evans, N.H. and Hetherington, A.M. (2001). Plant physiology: The ups and downs of guard cell signalling. Curr. Biol. 11:
R92-R94 with permission from Elsevier; Kudla, J., Batistič, O. and Hashimoto, K. (2010). Calcium signals: The lead currency of plant information processing. Plant Cell. 22: 541-563.
A model of the ionic fluxes that result in
calcium oscillations around the nucleus
during symbiotic interactions
Ca2+ oscillations contribute
to guard cell functions
How Ca2+
oscillations are
decoded remains
incompletely
resolved
© 2014 American Society of Plant Biologists
Summary: Calcium
• Much of a plant’s calcium may be in the form of calcium
oxalate crystals
• Free Ca2+ ion is mainly stored outside cytosol, in
apoplast and vacuole
• Calcium has a structural role in cell walls, particularly
pectin gelling
• Calcium has a signaling role conferred by transient
spikes in cytosol
© 2014 American Society of Plant Biologists
Macronutrients: Summary
• Macronutrients (N, P, K, S, Mg, Ca) are essential
elements that must be acquired from the environment
• Soil microbes affect nutrient availability and uptake
• Nutrient-specific transporters control uptake,
translocation and remobilization of mineral nutrients
• Some macronutrients are assimilated into organic
compounds
• Uptake and assimilation reactions are coordinated by
nutrient availability and demand
• Replenishment of soil nutrients is essential for high-
yielding agricultural systems
© 2014 American Society of Plant Biologists
Macronutrients - Summary
Diaz, R.J. and Rosenberg, R. (2008). Spreading Dead Zones and Consequences for Marine Ecosystems. Science. 321: 926-929.
The ecological impacts of agriculture are huge and
growing – most of these hypoxic regions arose
since 1950 and are attributed to human activities
© 2014 American Society of Plant Biologists
Gerland, P., Raftery, A.E., Ševčíková, H., Li, N., Gu, D., Spoorenberg, T., Alkema, L., Fosdick, B.K., Chunn, J., Lalic, N., Bay, G., Buettner, T.,
Heilig, G.K. and Wilmoth, J. (2014). World population stabilization unlikely this century. Science. 346: 234-237.
Macronutrients - Summary
9.6 billion
(2050)
7.2 billion
(2012)
10.9 billion
(2100)
WORLD POPULATION PROJECTION
Demand for food
will not slow down
during this century
We must find innovative
solutions to the challenge of
feeding the plants that feed us
© 2014 American Society of Plant Biologists
Ongoing research: Learn how plants
integrate different nutrient needs
Kellermeier, F., Armengaud, P., Seditas, T.J., Danku, J., Salt, D.E. and Amtmann, A. (2014). Analysis of the root system architecture of Arabidopsis provides a quantitative readout of crosstalk between nutritional signals.
Plant Cell. 26: 1480-1496. White, P.J., George, T.S., Dupuy, L.X., Karley, A.J., Valentine, T.A., Wiesel, L. and Wishart, J. (2013). Root traits for infertile soils. Front. Plant Sci. 4: 19.
How do roots optimize
growth when two or more
nutrients are limiting?
Cluster analysis of root
traits that enhance
acquisition of various
nutrients
Interactive effects
of nutrients and
daylength on root
growth
How can understanding
this integration support
breeding efforts?
© 2014 American Society of Plant Biologists
Ongoing research: Use best
practices for nutrient management
International Plant Nutrition Institute; See also American Society of Agronomy; Video link Plant Nutrition Institute
Manage nutrients
properly, using
the “4Rs”
Right Right
Right Right
NH4NO3 or
Urea?
How much?
Between rows? On
surface or deep?
Before planting?
During vegetative
growth phase?
Continue to develop technologies
to ensure optimal fertilizer use,
and make them affordable