Liang Xin, Li Shan-Wei, Wang Jin-Li, Zhao Hui-Min, Li Sha, Zhang Yan
Department of Plant Biology and Ecology, College of Life Sciences, Nankai University, Tianjin, 300071, China.
State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an, 271018, China.
Plant Reprod. 2023 Dec;36(4):349-354. doi: 10.1007/s00497-023-00475-6. Epub 2023 Aug 3.
Functional loss of Arabidopsis Sar1b with that of either Sar1a or Sar1c inhibits mitosis of functional megaspores, leading to defective embryo sac formation and reduced fertility. Vesicular trafficking among diverse endomembrane compartments is critical for eukaryotic cells. Anterograde trafficking from endoplasmic reticulum (ER) to the Golgi apparatus is mediated by coat protein complex II (COPII) vesicles. Among five cytosolic components of COPII, secretion-associated Ras-related GTPase 1 (Sar1) mediates the assembly and disassembly of the COPII coat. Five genes in Arabidopsis encode Sar1 isoforms, whose different cargo specificities and redundancy were both reported. We show here that Arabidopsis Sar1a, Sar1b, and Sar1c mediate the development of female gametophytes (FGs), in which Sar1b plays a major role, whereas Sar1a and Sar1c play a minor role. We determined that female transmission of sar1a;sar1b or sar1c;sar1b was significantly reduced due to defective mitosis of functional megaspores. Half of ovules in sar1a;sar1b/+ or sar1c;sar1b/+ plants failed to attract pollen tubes, leading to fertilization failure. The homozygous sar1a;sar1b or sar1c;sar1b double mutant was obtained by introducing either UBQ10:GFP-Sar1b or UBQ10:GFP-Sar1c, supporting their redundant function in FG development.
拟南芥Sar1b与Sar1a或Sar1c之一功能缺失会抑制功能大孢子的有丝分裂，导致胚囊形成缺陷并降低育性。不同内膜区室之间的囊泡运输对真核细胞至关重要。从内质网（ER）到高尔基体的顺向运输由II型被膜小泡蛋白复合物（COPII）囊泡介导。在COPII的五个胞质组分中，分泌相关的Ras相关GTP酶1（Sar1）介导COPII被膜的组装和解聚。拟南芥中有五个基因编码Sar1亚型，其不同的货物特异性和冗余性均有报道。我们在此表明，拟南芥Sar1a、Sar1b和Sar1c介导雌配子体（FG）的发育，其中Sar1b起主要作用，而Sar1a和Sar1c起次要作用。我们确定，由于功能大孢子有丝分裂缺陷，sar1a;sar1b或sar1c;sar1b的雌配子传递显著降低。sar1a;sar1b/+或sar1c;sar1b/+植株中一半的胚珠未能吸引花粉管，导致受精失败。通过导入UBQ10:GFP-Sar1b或UBQ10:GFP-Sar1c获得了纯合的sar1a;sar1b或sar1c;sar1b双突变体，支持了它们在FG发育中的冗余功能。
