Abstract: Cell cycle controls every phase of the whole plant life cycle from germination and growth to flowering and seed maturation. Whether the cell cycle could function normally depends on some cell cycle protein. The molecular mechanism of how the cell cycle controls lateral root genesis is still unclear. By screening the mutation library of Arabidopsis, we isolated one mutant named dig9 (drought inhibition of lateral root growth). The dig9 mutant has very severe phenotypes as shorten primary root, few lateral root, development retardation, smaller SAM, twisted leaf and non-stem. By map-based cloning, we located and cloned the DIG9 gene, which encodes APC8, a component of anaphase-promoting complex. We found the DIG9 protein located in nucleus in Arabidopsis protoplast. By qRT-PCR, we measured the expression levels in different tissues and found the gene was highly expressed in root. Further analysis was performed by promoter-GUS reporter system. The strong GUS signal was detected in root tip, lateral root and SAM. The few lateral root phenotype, but not shorten primary root phenotype, of dig9 mutant can be rescued by adding exogenous IAA. The dig9 mutant showed not sensitive to drought and salt stress treatment. These data illuminated that DIG9 can regulate lateral root genesis of Arabidopsis by affecting auxin biogenesis.

Key words: Arabidopsis thaliana, cell cycle, DIG9, lateral root, auxin

摘要： 在植物体内，细胞周期对于植物的萌发、生长、开花、结实等各个生长发育阶段具有重要作用。细胞周期正常运转需要依赖一些细胞周期蛋白，但是目前关于细胞周期蛋白调控根发育的分子机制还不清楚。通过筛选模式植物拟南芥的根发育异常突变体，分离鉴定了1个突变体dig9（drought inhibition of lateral root growth），该突变体表现为主根短、侧根少、发育迟缓、顶端分生组织变小、叶片扭曲、无主茎等表型。通过图位克隆，成功定位并克隆了DIG9基因，该基因编码一个细胞周期蛋白，是有丝分裂后期促进复合体的一个亚基APC8 （anaphase-promoting complex）。通过亚细胞定位发现DIG9定位于细胞核；qRT-PCR检测发现DIG9基因在根中有较高的表达量，进一步通过启动子-GUS报告系统发现DIG9在根尖、侧根和顶端分生组织等细胞分裂旺盛区域表达。外施IAA能恢复dig9突变体的侧根表型但不能恢复根短表型。dig9突变体对干旱及盐胁迫反应不敏感。研究结果表明DIG9基因可能通过影响IAA的产生来调控植物的侧根发育。

关键词: 拟南芥, 细胞周期, DIG9, 侧根, 生长素