Plant J|西南大学何光华教授团队揭示SHORT‐ROOT 1对水稻根系细胞分裂和管状分子发育至关重要

外囊是囊泡转运的关键因子，在真核生物中参与细胞分泌、细胞生长、细胞分裂和其他细胞学过程。Exo70是关键的外囊亚基。我们通过图位克隆和基因互补，获得了一个短根基因 sr1。Sr1是植物中一个保守的70结构域蛋白。sr1突变影响根系的整个发育过程，导致根系发育较短，不定根和侧根发育不良，木质部发育异常，引起矮化，水势和含水量下降。sr1主要在根中表达，但只在根分生组织和管状分子发育过程中表达。sr1突变体根的短小是由于分生组织细胞的减少。原位组蛋白 h4表达模式证实了根发育过程中细胞增殖受损。管状分子发育不良是由于相邻管状分支穿孔内径和穿孔间距明显减小所致。sr1突变体的膜输送被阻断，影响了根尖区的细胞分裂和管状分子的发育。SR1基因的研究将加深我们对外源70基因在水稻中功能的认识，并对今后植物根系发育相关分子机制的研究具有指导意义。

The exocyst is a key factor in vesicle transport and is involved in cell secretion, cell growth, cell division, and other cytological processes in eukaryotes. EXO70 is the key exocyst subunit. We obtained a gene SHORT‐ROOT, SR1, through map‐based cloning and genetic complementation. SR1 is a conserved protein with an EXO70 domain in plant. SR1 mutation affected the whole root‐development process, producing shorter radicles, adventitious roots, and lateral roots, abnormal xylem development, causing dwarfing, and decreasing the water potential and moisture content. SR1 was largely expressed in the roots, but only in developing root meristems and tracheary elements. The shortness of the sr1 mutant roots was caused by the presence of fewer meristem cells. The in situ histone H4 expression patterns confirmed that cell proliferation during root development was impaired. Tracheary element dysplasia was caused by marked decreases in the inner diameters of and distances between the perforations of adjacent tracheary elements. The membrane transport of the sr1 mutants was blocked, affecting cell division in the root apical region and root tracheary element development. The study of SR1 will deepen our understanding of the function of EXO70 genes in rice and guide future studies on the molecular mechanisms involved in plant root development.

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