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6月，中国科学院西双版纳热带植物园的陈江华课题组在New Phytologist发表了一篇题为A study of male fertility control in Medicago truncatula uncovers an evolutionarily conserved recruitment of two tapetal bHLH subfamilies in plant sexual reproduction的文章，揭示了bHLH转录因子EAN1调控蒺藜苜蓿的雄性不育机制。
摘 要
雄性不育是植物育种和杂交种子生产的重要工具。植物的雄性不育突变体主要是由孢子体型或配子体型的花药组织发育异常引起的。绒毡层是重要的孢子体型组织，为花粉发育提供营养，其发育异常会引起花粉败育。已有研究报道bHLH转录因子调控被子植物的绒毡层退化，但这些调控绒毡层发育的基因在陆生植物中的进化模式尚不清楚。该研究以豆科模式植物蒺藜苜蓿为材料，通过细胞、分子、生化和进化分析相结合的方法，研究植物的雄性不育机制。蒺藜苜蓿雄性不育突变体ean1表现为营养期植株生长正常，而生殖期雄性不育。EAN1编码bHLH转录因子，特异调控绒毡层的发育。进化分析发现EAN1属于bHLH转录因子II类亚家族，与III（a+c）亚家族成员形成异源二聚体，这表明在被子植物绒毡层发育中，II和III（a+c）类bHLH转录因子形成异源二聚体的机制是保守的。
Phenotypic analysis of Medicago truncatula WT and ean1-1 mutant.
Abstract
Male sterility is an important tool for plant breeding and hybrid seed production. Male‐sterile mutants are largely due to an abnormal development of either the sporophytic or gametophytic anther tissues. Tapetum, a key sporophytic tissue, provides nutrients for pollen development, and its delayed degeneration induces pollen abortion. Numerous bHLH proteins have been documented to participate in the degeneration of the tapetum in angiosperms, but relatively little attention has been given to the evolution of the involved developmental pathways across the phylogeny of land plants.A combination of cellular, molecular, biochemical and evolutionaryanalyses was used to investigate the male fertility control inMedicago truncatula.We characterized the male‐sterile mutantempty anther1(ean1) and identified EAN1 as a tapetum‐specific bHLH transcription factor necessary for tapetum degeneration. Our study uncovered an evolutionary conserved recruitment of bHLH subfamily II and III(a+c)1 in the regulation of tapetum degeneration. EAN1 belongs to the subfamily II and specifically forms heterodimers with the subfamily III(a+c)1 members, which suggests a heterodimerization mechanism conserved in angiosperms.Our work suggested that the pathway of two tapetal‐bHLH subfamilies is conserved in all land plants, and has been likely established prior to the divergence of the spore‐producing land plants.论文链接：/10.1111/nph.16770
