The International Journal of Plant Reproductive Biology 10(1) Jan., 2018, pp.14-25

DOI 10.14787/ijprb.2018 10.1.14-25

B-chromosomes in Gymnosperms-A Review

Elena N. Muratova

V.N. Sukachev Institute of Forest, Russian Academy of Sciences, Siberian Branch. Krasnoyarsk, Russia

e-mail: elena-muratova@ksc.krasn.ru

Received: 25.09.2017; Revised: 27.11.2017; Accepted and Published online: 01.12.2017

ABSTRACT

Literature on B-chromosomes in Gymnosperms has been reviewed. Among gymnosperms accessory chromosomes are reported in representatives of families Cupressaceae, Taxodiaceae, Ephedraceae, Pinaceae, and possibly in Podocarpaceae and Taxaceae. The number of species with B-chromosomes is more than 35. B-chromosomes are distinct in morphology. They follow specific of behavior mitosis and meiosis, character of inheritance.

Keywords : B-chromosome, supernumerary chromosomes, additional chromosomes, A-chromosomes, karyotype, gymnosperms.

B-chromosomes (Bs, supernumerary, additional) are extra gymnosperm species belonging to families Cupressaceae chromosomes to the normal (basic) set (called A- (including Taxodiaceae), Ephedraceae, Pinaceae, and chromosomes or As). They show variation between and within possibly also in Podocarpaceae and Taxaceae. populations, individuals and cells. They are found in vertebrate and invertebrate animals and fishes. Among plants they have the information on B-been reported in fungi, ferns, gymnosperm and angiosperms chromosomes in gymnosperms is summarized in Table. (both monocots and eudicots) (Muntzing 1958, 1967, 1974, In the family Cupressaceae (including Taxodiaceae) B-Battaglia 1964, Orlov 1974, Moshkovich 1979, Rees 1974, chromosomes occur in Sequoia sempervirens, Metasequoia Jones 1975, 1995, 2017, Volobuev 1981, Jones and Rees 1982, glyptostroboides, Cunninghamia lanceolata, Taiwania Muratova 2000, Palestis et al. 2004, Jones et al. 2008, Kunakh flousiana, Taxodium ascendens, and two species of 2010, Houben et al. 2011, Borisov 2014, D’Ambrosio et al. Cupressus. In family Ephedraceae supernumerary 2017, and others). Therefore, supernumerary chromosomes chromosomes exist in E. major and fragment in E. foliata. are widely distributed among plants and animals and are a , general phenomenon in eucaryotes.

For long time it was believed that in woody plants B- In the genus Larix study chromosomes are absent. The reason for this belief was cases of B-chromosomes availability were registered in L. paucity of information about cytology of this difficult group of gmelinii, L. sibirica and L. sukaczewii. In genus Pinus, B-plants. Today B-chromosomes are known to exist in many chromosome has been described in P. sylvestris. Among gymnosperms. conifers in exist half the species of genus Picea B-

chromosomes occur. At present B-chromosomes were found The aim of this in 19 species and interspecific hybrid P. x fennica (Table).

review is to present at one place all the existing data on B- Chromatin fchromosomes of gymnosperms generated by different investigators. As for other gymnosperms,

Among gymnosperms B-chromosome was first reported in a cypress – Cupressus glabra (Hunziker 1958, 1961). There In family Podocarpaceae 7 supernumerary after B-chromosome was found in hexaploid Sequoia chromosomes were detected in one male tree of Podocarpus sempervirens (Saylor and Simons 1970); 1-2 B-chromosomes macrophyllus; many species of the genus Podocarpus are were discovered in diploid Cupressus arizonica (Thomas and n opinion of authors (Hizume et al., 1988), B-Goggans 1972). However, as early as in 1932, during study of chromosomes play no role in sex detrmination. But some meiosis in Taxus canadensis fragment was described (Dark, cytogeneticists point out similarity between B-chromosomes 1932). and sex chromosomes in meiotic behaviour, size, morphology

and heteropycnocity (Amos and Dover 1981, Jones and Rees ( 1982, Green 1990, Camacho et al. 2000). Sex chromosomes

Greater attention to B-chromosomes in gymnosperms has have been proposed as ancestors of B-chromosomes (Hewitt been paid since 1970s, when 1973).

Picea obovata in The highest number of B-chromosomes per cell recorded Russia (Kruklis 1971a, b) and in P. sitchensis in North in gymnosperms is 10 in Ephedra major (Ershadi et al. 2003); America (Moir and Fox 1972). Over the years B- 7 B-chromosomes have been reported in Podocarpus chromosomes have been discovered in more than 30 macrophyllus (Hizume et al. 1988). Some provenances of

With the progress of karyological investigations, the number of species with Bs is steadily increasing.

In the largest and most important economically family Pinaceae B-chromosomes exist in species of Larix, Picea, Pinus and possibly, Pseudotsuga and Tsuga.

After publication of the last review on B-chromosomes in gymnosperms (Muratova 2000), new data appeared and they required interpretation.

ragments resembling B-chromosomes exist in Pseudotsuga menziesii and Tsuga canadensis.

chromatin fragment reported in Taxus canadensis (Taxaceae) is not yet to be confirned as B chromosome.

dioecious. I

According to modern concepts, it could well be an additional chromosome. Later, a fragment resembling a B-chromosome was also found in Ephedra foliata Rao, 1968).

they were found almost simultaneously in two species of spruce – in

EPR R OT DN UAL CP T IF VEO BYT IOEI L

C O

O G

S I SE TH ST

Picea glauca and P. albertiana have 6 B-chromosomes (Rees But majority of spruce species investigated have both et al. 1977, Teoh and Rees 1977), P. glehnii and P. sitchensis – types of B-chromosomes: (Moir and Fox 1972, Teoh and Rees 5 (Moir and Fox 1971, Teoh and Rees 1977, Kean et al. 1982), 1977, Kean et al. 1982, Liu and Li 1985, Hizume et al. 1991, P. obovata, P. abies and Sequoia sempervirens have 4 each Gamaeva 1992, Shi and Wang 1994, Muratova and Frolov (Kruklis 1971a,b, Broka 1990, Muratova and Vladimirova 1995, Butorina and Bogdanova 2001, Muratova et al. 2001a,b, 2010a, Pimenov et al. 2012, Hizume et al. 2014, Tashev et al. 2002, 2008, Vladimirova et al. 2003, Karpyuk and Muratova 2014, 2015). Karyotypes of Picea species with varying 2005, Shibata and Hizume 2008, Kvitko et al. 2009, number of B-chromosome are given on the Fig. 1. Goryachkina et al. 2013). The two types of B-chromosomes

B-chromosomes of gymnosperms are smaller than of P. ajanensis are shown in Fig. 2. chromosomes of the normal complement. Usually the length of B-chromosomes of conifers (Picea, Pinus and Larix) is 25-30% that of A-chromosomes. The B-chromosomes of Picea species are either meta- or submetacentric, which have been designated as B and B respectively (Teoh and Rees 1977, Liu 1 2

and Li 1985, Hizume et al. 1989, Muratova 2000). P. jezoensis, P. microsperma, P. breweriana and P. schrenkiana have metacentric Bs (Hizume et al. 1989, Vladimirova et al. 2007, Karpyuk et al. 2009) and P. hondoensis have a b

Fig. 2–Two types of B-chromosomes in Picea ajanensis : a – submetacntric of Bs (Hizume and Kuzukawa 1995). metacentric type; b – submetacentric type. Horizontal line shows location of centromere.

Fig. 3– AgNO -bands in B-chromosomes of Picea obovata.3

Many others species of gymnosperms (Larix gmelinii, L. sukaczewii, P. sylvestris, Cupressus arizonica, Cunninghamia lanceolata, Sequioa sempervirens) have also B-chromosomes of the same morphology (Saylor and Simons 1970, Thomas and Goggans 1972, Butorina et al. 1979, Liu and Li 1985, Fang 1986, Muratova 1991, 1994, Kalashnik 1994, Farukshina and Putenikhin 2004, Hizume et al. 2014). It has been proposed that submetacentric B-chromosomes have originated as a result of pericentric inversion of the metacentric (Teoh and Rees 1977, Kean et al. 1982). Other

Fig. 1. Karyotypes of spruce species with B-chromosomes: variants of B-chromosomes exist in Picea glehnii. This a – P. obovata with one B-chromosome (2n=24+1B); b – P. obovata with species has B-chromosomes of five morphological types two B-chromosomes (2n=24+2B); c – P. obovata with three B-

(Muratova and Vladimirova 2001a); large metacentric chromosomes (2n=24+3B); d – P. ajanensis with one B-chromosome (2n=24+1B); e – P. meyeri with three B-chromosomes (2n=24+3B). chromosome, two short Bs – meta- and submetacentric, one Material stained with acetohematoxylin. Arrows point to the B- small metacentric and very small submetacentric ones. Small chromosomes. Bar indicates 5 mm.

b

a

c d

e

2018 15B-chromosomes in Gymnosperms-A Review

metacentric B-chromosomes has been reported in Ephedra B-chromosomes of gymnosperms do not bear secondary major (Chouhdry and Tanaka 1983). constriction and satellites. Silver-staining has revealed bright

B-chromosomes can be eu- or heterochromatic. In bands in B-chromosomes of Siberian spruce Picea obovata gymnosperms, B-chromosomes of Picea glauca, P. sitchensis, (Fig. 1f) indicating the possibility of its B-chromosomes and P. obovata are heterochromatic which are visibe as bearing nucleolar-organizing ability (Muratova 2000, chromocenters at interphase (Moir and Fox 1972, Teoh and Vladimirova 2002). However application of fluorescent in Rees 1977, Kean et al. 1982, Muratova et al. 2002). Accessory situ hybridization (FISH) with probes of 5S and 45S ribosomal chromosomes of Cupressus arizonica and Pinus sylvestris have RNA genes in P. pungens has revealed absence of these genes. high content of heterochromatin (Thomas and Goggans 1972, These data were in agreement with results of Japanese Butorina et al. 1979). B-chromosome of Sequoia sempervirens, investigators: B-chromosomes of P. jezoensis var. hondoensis, Picea jezoensis, P. hondoensis P. brachytyla are euchromatic P. engelmannii, P. koyamai also have not loci of 5S rDNA or (Saylor and Simons 1970, Hizume et al. 1989, 1991). In 18 S rDNA (Hizume Kuzukawa 1995, Shibata and Hizume metaphase B-chromosomes of some gymnosperms are more 2008). condensed contrast to A-chromosomes (Teoh and Rees 1977, Fluorescent banding for B-chromosomes of some Picea Muratova et al. 2002, Vladimirova 2002). species displayed neither CMA nor DAPI-bands in P.

Fig. 4–Fluorescent in situ hybrydization (FISH) of Picea pungens with probes of 5S and 45S ribosomal RNA genes. B-chromosome has no signals.Photo provided by Olga Goryachkina, Krasnoyarsk, Russia.

16 The International Journal of Plant Reproductive Biology 10(1) Jan. 2018, pp.14-25

jezoensis var. jezoensis, P. jezoensis var. hondoensis and P. Extensive to karyological study of Siberian spruce (Picea brachytyla var. complanata (Hizume et al. 1989, 1991). DAPI obovata) from in European part of Russia, the Urals, North is fluorescent stain for AT-rich regions in DNA, CMA Eastern Kazakhstan, Siberia has been carried out by (chromomycin A ) is stain for GC-rich regions in DNA. B- cytologists of Russia and former USSR (Kruklis 1971a,b, 3

chromosomes in P. glehnii had no CMA-bands, but possessed Pravdin et al. 1976, 1978, Shershukova 1978, Medvedeva and the DAPI-band at proximal interstitial region (Hizume et al. Muratova 1987, Broka 1990, Farukshina et al. 1997, Muratova 1988). B-chromosomes of Sequoia sempervirens had several 2000, 2011a,b, 2014, Muratova and Vladimirova 2001b, weak CMA-bands (Hizume et al., 2014). Muratova et al. 2001a, 2002, Vladimirova 2002, Vladimirova

B-chromosomes differ from A-chromosomes in the and Muratova 2005, Kalashnik 2008, 2009, 2010, Borisov and organization of genetic material. B-chromosomes of different Muratova 2010, Sedel’nikova et al. 2011, and others). organisms include many highly repeated DNA sequences with Investigations were carried out in natural populations of regular functions but do not bear structural genes. B- Siberian spruce from regions of West, Central and East chromosomes are filled with ribosomal, mitochondrial, and Siberia. More than 50 natural populations of this species were virus similar structures; they have pseudogenes (Camacho et studied and In al. 2000, Houben et al. 2011, 2013, 2014). In general, the western populations of Siberian spruce B-chromosomes are composition of the DNA of B-chromosomes is similar to that rare. In European part of Russia Bs are absent. Populations of the A-chromosomes. But heterochromatin of B- from Southern Urals and East Kazakhstan are the most chromosomes differs in DNA composition from DNA of A- western where B-chromosomes have been found. In related chromosomes (Jones and Rees 1982). species P. abies growing in Europe 1-4 B-chromosomes were

Usually presence of B-chromosomes doesn’t affect the found recently (Pimenov et al. 2012, Tashev et al. 2014, 2015). phenotype but high numbers of supernumerary chromosomes P. x fennica, hybrid between P. obovata and P. abies has one B-are unfavourable (Moshkovich 1979, Jones and Rees 1982, Fox chromosome (Farukshina et al. 1997, Muratova et al. 2002, 1987, Jones 1995, Camacho et al. 2000, Jones and Houben 2003, Kalashnik 2008, 2009, 2010). B-chromosomes are in the Jones et al. 2008, Houben et al. 2011). In gymnosperm plant populations of eastern parts of species area, in Central and Sitka spruce (Picea sitchensis) effect of the B-chromosomes on Eastern Siberia especially, in extreme conditions (Broka 1990, growth rate in was not observed (Moir and Fox 1976). In many Muratova 2000, Muratova et al. 2002). In addition, B-cases supernumerary chromosomes have negative influence on chromosomes are widely spread in introductive stands fertility and viability. In Sitka spruce B-chromosomes delay the (Vladimirova and Muratova 2005, 2006).both male and female flowering (Kean et al. 1982). B-chromosome has widespread distribution in North

B-chromosomes affect nuclear phenotype, genome American species of spruce e.g. – P. sitchensis and P. glauca. function, duration of cell cycle, cell size, genetic activity, In P. glauca from western and eastern regions of Canada 48 of nuclear DNA content and the behaviour of A-chromosomes the 51 populations investigated carried Bs; in two of these Bs during meiosis (Moir and Fox 1975, Teoh and Rees 1976, were found in more than 90% plants (Teoh and Rees 1977). In 1977, Jones and Rees 1982, Broka 1990, Jones 1995, P. sitchensis from the west coast of North America (Canada Camacho et al. 2000, Kunakh 2010, Houben et al. 2011, 2013, and USA) they were present in 29 of the 40 populations (Moir 2014, Borisov 2014). During meiosis they affect the and Fox 1977). Many authors assumed that presence of B-distribution and frequency of chiasmata. Bs don’t recombine chromosomes in conifers can be connected with unfavourable with A-chromosomes. Studies on B-chromosomes ecological conditions of the areas where they grow (Pravdin et transmission in Siberian spruce (Picea obovata) and Sitka

al. 1976, Moir and Fox 1977, Teoh and Rees 1977, Jones and spruce (P. sitchensis) has revealed that they are transmitted

Rees 1982, Muratova 2000, Sedel’nikova et al. 2011). It is through both female and male tracks (Kean et al. 1982,

possibly plants with B-chromosomes are more polymorphic Kruklis 1982, Vladimirova and Muratova 2002). However, in

and more adaptive to changing environment in contrast with P. obovata B-chromosomes mainly inherited from mother

plants without them.plants (Kruklis 1982, Vladimirova and Muratova 2002). B-chromosomes impact adaptive plasticity to species The number of B-chromosomes in plants is not stable like

(Teoh and Rees 1977, Moshkovich 1979, Jones and Rees those of A-chromosomes. They occur in both diploid and 1982, Muratova 2000, Kunakh 2010, Borisov 2014). Origin polyploid species. Some species show availability of B-and fixing of B-chromosomes give the possibility to wide chromosomes in the central parts of area as well as in labile genome system and to raise adaptive possibilities of peripheral small isolated populations. It is generally agreed organisms. It is possible plants including B-chromosomes are that B-chromosomes are derived from A-chromosomes more polymorphic than plants without them and more through fragmentation, genetic rearrangement and gene adaptive to changing environment. But this hypothesis needs silencing (Jones and Rees 1982, Camacho et al. 2000, Kunakh

2010, Houben et al. 2011, 2013, 2014, Borisov 2014).

B-chromosomes were found in half of them.

to be confirmed on the basis of new investigations.

2018 17B-chromosomes in Gymnosperms-A Review

Taxon Number

of chro-

mosomes,

2n

1 2 3

CUPRESSACEAE (including Taxodiaceae)

Cunninghamia lanceolata (Lamb.) Hook. fil. 22+1-2B Han et al. 1980, 1984, Fang and Hsu (Xu) 1986, Chen and Ye 1985.

Cupressus arizonica Greene 22+1-2B Thomas and Goggans 1972.

C. glabra Sudw. 22+1B Hunziker 1958, 1961.

Metasequoia glyptostroboides Hu et Cheng. 22+1B Fang 1986.

Sequoia sempervirens (Lamb.) Endl. 66+1B Fozdar and Libby 1968, Saylor and Simons 1970

66+B’s

66+4B

Taiwania flousiana Gauss. 22+1B Fang 1986.

Taxodium ascendens Brongn. 22+2B Huang and Hsu (Xu) 1984.

EPHEDRACEAE

E. foliata Boiss. ex C. A. Mey 14+f Rao 1968.

E. major Host 14+2B Chouhdry and Tanaka 1983, Chouhdry 1984.

PINACEAE

Larix gmelinii (Rupr.) Rupr. 24+1B Muratova 1991, 1994, 1995, 2000, 2011a,b, Muratova and Sedel’nikova 2000; Milyutin et al. 2002, 2004, Muratova et al. 2007, 2008, Sedel’nikova et al. 2011.

L. sibirica Ledeb. 24+1? Muratova et al. 2007, 2008, Sedel’nikova et al. 2005, 2011, Syzikh et al. 2006, Sedel’nikova and Pimenov 2007, Kvitko et al. 2009, Muratova 2011a,b.

L. sukaczewii Dylis 24+1B Farukshina and Putenikhin 2004, Putenikhin et al. 2004.

Picea abies (L.) H. Karst. 24+1-4? Pimenov et al., 2012; Tashev et al. 2014, 2015.

P. abies ssp. obovata (Ledeb.) Hulten (P. obovata Ledeb.) 24+1B? Druškovic and Zupancic 1997.

P. ajanensis (Lindl. et Gord.) Fisch. ex Carr. 24+1-3B Il’chenko and Gamaeva 1991, Gamaeva 1992, Muratova and Frolov 1995, Muratova and Sedel’nikova 2000, Muratova et al. 2001a,b, 2002, 2008, Vladimirova et al., 2003, Muratova 2011a,b, 2014, Sedelnikova et al. 2011.

P. brachytyla var. complanata (Masters) W. C. Cheng et 24 + 1B Hizume et al. 1991.

Rehd. (P. complanata Masters)

P. breweriana S. Watson 24+1B Vladimirova et al. 2007, Sedel’nikova et al. 2011, Muratova 2011a, b, 2014.

P. engelmannii (Parry) Engelm. 24+1B Shibata and Hizume 2008.

24+1-2B Teoh and Rees 1977.

P. x fennica (Regel) Kom. 24+1B Farukshina et al. 1997, Muratova et al. 2002, Sedel’nikova et al. 2011, Muratova 2011a,b, 2014, Kalashnik 2008, 2009, 2010.

P. glauca (Moench.) Voss 24+1B Nkongolo 1996, Tremblay et al. 1999, Butorina and Bogdanova 2001.

24+1- 3B Goryachkina et al. 2013,

24 +1- 6B Teoh and Rees 1977, Rees et al. 1977.

P. glauca var. albertiana St. Br. Sarg. (P. albertiana St. Br.) 24 + 1-6? Teoh and Rees 1977.

P. glehnii (Fr. Schmidt) Mast. 24+1-2B Hizume 1988, Hizume et al. 1988.

24+1–5B Muratova and Sedelnikova 2000, Muratova and Vladimirova 2001a, Muratova et al. 2001a, b, 2002, 2008, Sedel’nikova et al. 2011, Muratova 1999, 2011a,b, 2014.

P. jezoensis (Siebold et Zucc.) Carr. 24+1B Hizume et al. 1989, Nkongolo 1999.

P. jezoensis var. hondoensis (Mayr) P.A. Schmidt 24+1–2B Hizume and Kuzukawa 1995, Hizume et al. 1989; Shibata and(P. hondoensis Mayr) Hizume 2008.

P. koyamae Shiras. 24+1-2? Shibata and Hizume 2008, Kvitko et al. 2009, Sedel’nikova et al. 2011, Muratova 2011a, b, 2014, Goryachkina et al. 2013.

References

18 The International Journal of Plant Reproductive Biology 10(1) Jan. 2018, pp.14-25

Taxon Number References

of chro-

mosomes,

2n

1 2 3

P. jezoensis var. microsperma (Lindl.) W.C. Cheng et L. K. Fu (P. microsperma Carrière)

P. likiangensis var. linzhiensis W.C. Cheng & L.K. Fu 24+1B Li et al. 2001.

[P. linzhiensis (W.C. Cheng & L.K. Fu) Rushforth]

P. meyeri Rehd. 24+1B Goryachkina et al. 2013.

24+1–2B Liu and Li 1985, Lai et al. 1986, Ge et al. 1987, Xu et al. 1994.

24+1–3B Vladimirova et al. 2003, Muratova et al. 2008, Karpyuk and Muratova 2005, Sedel’nikova et al. 2011, Muratova 2011a,b, 2014.

P. obovata Ledeb. 24+1B Kvitko et al., 2009.

24+1–2B Pravdin et al. 1978, Shershukova 1978, Medvedeva and Muratova 1987, Muratova and Sedel’nikova 2000, Sedel’nikova et al. 2000, 2004.

24+1–3B Pravdin et al. 1976, Muratova et al. 1991, 2001a, b, 2002, 2008, Muratova 2000, 2011a, b, 2014, Muratova and Vladimirova 2001b, Vladimiriva 2002, Vladimirova and Muratova 2002, 2005, 2006, Vladimirova et al., 2003, 2007, Borisov and Muratova 2010, Sedel’nikova et al. 2011, Bazhina et al. 2017.

24+1–4B Kruklis 1971a, b, 1982, Broka, 1990.

P. pungens Engelm. 24+1B Muratova et al. 2002, Vladimirova et al. 2007, Sedel’nikova et al. 2011, Muratova 2011a,b, 2014.

P. schrenkiana Fisch. et C. A. Mey 24+1B Muratova et al. 2002, 2008, Karpyuk at al. 2009, Sedel’nikova et al. 2011, Muratova 2011a,b, 2014.

P. sitchensis (Bong.) Carr. 24+1-2B Goryachkina et al. 2013.

24+1-5B Moir and Fox 1972, 1975, 1976, 1977, Teoh and Rees 1977, Kean 1982, Kean et al., 1982.

P. wilsonii Mast. 24+1B Shi and Wang, 1994.

24+1–2B Liu and Li 1985, Yang et al. 1994.

Pinus sylvestris L. 24+1B Butorina et al. 1979, Molotkov et al. 1989, Kalashnik 1994.

Pseudotsuga menziesii Mirb. Franco 26+1B? Owens 1967.

Tsuga canadensis (L.) Carrière 24+1B? Gavrilov and Butorina 2005.

PODOCARPACEAE

Podocarpus macrophyllus (Thunb.) Sweet, male plant 37+7B Hizume et al. 1988.

TAXACEAE

T. canadensis Marsh. 24+f Dark 1932.

24 + 1B Liu and Li 1985.

CONCLUSION Acknowledgements—The reported study was funded by Russian Foundation of Basic Research according to the

Among gymnosperms accessory chromosomes are found research project No 18-04-00051. I’d like to thank Olga

more than 35 species in families Cupressaceae, Taxodiaceae, Goryachkina (Krasnoyarsk, Russia) for providing

Ephedraceae, Pinaceae, and possibly in Podocarpaceae and photomicrographs.

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