光/温敏核不育系的不育机理及两系杂交稻的发展与展望
Sterility Mechanism of Photoperiod/Thermo-sensitive Genic Male Sterile Lines and Development and Prospects of Two-line Hybrid Rice
光温敏型雄性不育是高温下花粉形成相关基因突变导致的不育。不育系在低温或短光照条件下形成有功能的花粉从而恢复育性，因此是一个细胞学的问题。A: 在限制条件（高温/长日照）下，花粉形成经历从四分体壁到花粉壁的细胞壁转换过程。光温敏相关基因保证了细胞壁的转换。B: 在限制条件（高温/长日照）下，这些光温敏基因的突变导致细胞壁保护作用下降，无法满足小孢子发育的需求，导致花粉破裂，雄性不育。C: 温和条件（低温/短日照）下，缓慢发育导致小孢子发育对细胞壁保护的要求下降。在此情况下，光温敏不育系中的小孢子在基因突变的情况下仍能获得足够的保护，从而形成有功能的花粉，恢复育性。水稻与拟南芥光温敏基因存在很大的差异，提示水稻等作物除了缓慢发育以外还存在其他的机制。图中绿色字体表示拟南芥中发现的光温敏不育基因，黄色字体表示水稻中发现的光温敏不育基因。花粉示意图中的箭头指向表示光温敏基因的影响的细胞壁成分。红色箭头表示野生型光温敏基因可以提供完整的保护。虚线箭头表示光温敏不育系无法提供完整功能。蓝色箭头表示在温和条件下光温敏基因可以为植物提供足够保护。
P/TGMS is caused by genetic mutations related to pollen formation under high temperature. The P/TGMS line forms functional pollen and restores fertility under low-temperature or short-light conditions, making it a cytological issue. A, Under restrictive conditions (high temperature/long photoperiod), the pollen undergoes a cell wall transition process from tetrad wall to pollen wall. P/TGMS genes ensure the proper transition of the cell wall. B, Under restrictive conditions (high temperature/long photoperiod), mutations in these P/TGMS genes reduce the protection of cell wall, leading to insufficient support for the development of microspores and causing pollen rupture, resulting in male sterility. C, Slow development under permissive conditions (low temperature/short photoperiod) reduces the requirements for cell wall protection during microspore development. P/TGMS lines are able to meet the requirements for their wall protection and thus support their development into functional pollens, leading to restored fertility. There are significant differences between rice and Arabidopsis in P/TGMS genes, suggesting the presence of a distinct P/TGMS mechanism in rice other than slow development. Green font represents P/TGMS genes in Arabidopsis. Yellow font represents P/TGMS genes in rice. The arrows indicate the impact of P/TGMS genes on cell wall components. The red arrow indicates that the P/TGMS gene can provide full protection in the wild type. The dotted arrow indicates the insufficient protection provided by P/TGMS lines. Blue arrows indicate that under permissive conditions, P/TGMS genes can provide sufficient protection for plants.
