The mysterious sex chromosomes of haploid plants.
The mysterious sex chromosomes of haploid plants.
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单倍体植物神秘的性染色体。
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单倍体植物（包括苔藓和苔藓植物）的性染色体比二倍体植物的性染色体研究要少得多。然而，人们早就知道，苔藓植物中具有独立性别个体的情况比二倍体植物更为常见（Perley 和 Jesson 2015）（其中雌雄异株物种的比例一直估计在 5% 左右（参见 Charlesworth 1985，Renner 2014，Yampolsky 和 Yampolsky 1922）。这两种类型的一些植物可能不具有遗传性别决定（Pannell） 1997 年，Tanurdzic 和 Banks 2004，Zimmerman 1991），但苔藓植物的早期细胞遗传学研究观察到了异形性染色体（Allen 1917；1919），雄性和雌性配子体的核型明显不同。尚无公正的估计，研究的物种数量很少，但数据（由 Allen（1945）和Renner 等人（2017））表明，大约一半的有性苔藓植物物种具有明显不同的性染色体，至少与雌雄异体二倍体被子植物中的性染色体一样多（Ming 等人，2011，Westergaard 1958）。因此，总体而言，可用于研究性染色体的苔藓植物比被子植物物种多得多。然而，令人惊讶的是，苔藓植物性染色体却被忽视了（图 1）。 1），特别是作为单倍体生命周期阶段的优势，配子体阶段，预测了与二倍体植物或动物的性染色体的有趣差异（下面的表1）。此外，自由生活的配子体很大，并且可以被收集，并且它们的基因组序列提供阶段性数据，允许两个性染色体序列分别组装，这在二倍体中是困难的，因为Y染色体必须在XY雄性中组装（或在有雌性的物种中的ZW雌性中）。苔藓植物性染色体序列提供了测试单倍体和二倍体系统之间预测差异的机会（Bull Bull 指出，在单倍体植物生命周期中，二倍体合子“由雌性配子和雄性配子结合产生，因此总是杂合的，XY。因此，如果非重组，则完全产生单倍体孢子”。性别连锁区域存在，雄性和雌性决定版本都是非重组的，与二倍体开花植物（或具有 XY 系统的动物）不同，后者具有完全 Y 连锁区域，而 X 连锁区域在雌性中交叉，为了强调这种差异，雌性和雄性配子体中的性染色体不再分别称为 X 和 Y，而是命名为 U 和 V（图 2）。二倍体中性别之间的重组不对称性可以解释原因。只有 Y 染色体会发生遗传退化（Muller 1914），因为 Y 连锁突变不能交叉。
The sex chromosomes of haploid plants, including mosses and liverworts (members of the bryophytes) have been much less studied than those of diploid plants. However, it has long been known that having separate sexed individuals is much commoner in bryophytes (Perley and Jesson 2015), than in diploid plants (in which the proportion of dioecious species has consistently been estimated at around 5%(see Charlesworth 1985, Renner 2014, Yampolsky and Yampolsky 1922). Some plants of both types may not have genetic sex-determination (Pannell 1997, Tanurdzic and Banks 2004, Zimmerman 1991), but early cytogenetic studies in bryophytes observed heteromorphic sex chromosomes (Allen 1917; 1919), with the karyotypes of male and female gametophytes differing clearly. Unbiased estimates are not yet available, and species numbers studied are small, but the data (reviewed by Allen (1945) and Renner et al.(2017)) suggest that around half of separate sexed bryophyte species have visibly different sex chromosomes, at least as many as in dioecious diploid angiosperms (Ming et al. 2011, Westergaard 1958). Overall, therefore, many more bryophyte than angiosperm species are available for studying sex chromosomes.Bryophyte sex chromosomes have, however, been surprisingly neglected (Fig. 1), especially as the dominance of the haploid life cycle stage, the gametophyte stage, predicts interesting differences from the sex chromosomes of diploid plants or animals (Table 1 below). Moreover the free-living gametophytes are large, and can be collected and their genome sequences provide phased data, allowing the two sex chromosome sequences to be assembled separately, which is difficult in diploids where the Y chromosome has to be assembled in the XY males (or in ZW females in species with female heterogamety). Bryophyte sex chromosome sequences offer the opportunity to test the differences predicted between haploid and diploid systems (Bull 1978). Bull pointed out that, in the haploid plant life cycle, the diploid zygote ‘is produced by the union of a gamete from a female and one from a male and is therefore always heterozygous, XY. The diploid merely produces haploid spores’. Consequently, if a non-recombining, completely sex-linked region exists, both the male-and female-determining versions are nonrecombining, unlike in diploid flowering plants (or animals with XY systems), which have fully Y-linked regions, while the X-linked region crosses over in females. To emphasise this difference, the sex chromosomes in female and male gametophyte are no longer called X and Y, respectively, but are named U and V (Fig. 2). The recombination asymmetry between the sexes in diploids can explain why only Y chromosomes undergo genetic degeneration (Muller 1914). Since Y-linked mutations cannot cross over
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影响因子：
64.8
作者：
Sturgill, David;Zhang, Yu;Oliver, Brian
通讯作者：
Oliver, Brian
影响因子：
3
作者：
Perley, Danielle S.;Jesson, Linley K.
通讯作者：
Jesson, Linley K.
影响因子：
3.8
作者：
Pannell, J
通讯作者：
Pannell, J
DOI：
10.1016/j.cub.2021.10.023
发表时间：
2021-12-20
期刊：
Current biology : CB
影响因子：
--
作者：
Iwasaki M;Kajiwara T;Yasui Y;Yoshitake Y;Miyazaki M;Kawamura S;Suetsugu N;Nishihama R;Yamaoka S;Wanke D;Hashimoto K;Kuchitsu K;Montgomery SA;Singh S;Tanizawa Y;Yagura M;Mochizuki T;Sakamoto M;Nakamura Y;Liu C;Berger F;Yamato KT;Bowman JL;Kohchi T
通讯作者：
Kohchi T
影响因子：
13.6
作者：
Carey SB;Jenkins J;Lovell JT;Maumus F;Sreedasyam A;Payton AC;Shu S;Tiley GP;Fernandez-Pozo N;Healey A;Barry K;Chen C;Wang M;Lipzen A;Daum C;Saski CA;McBreen JC;Conrad RE;Kollar LM;Olsson S;Huttunen S;Landis JB;Burleigh JG;Wickett NJ;Johnson MG;Rensing SA;Grimwood J;Schmutz J;McDaniel SF
通讯作者：
McDaniel SF