Gonzalez Nathalie, Gévaudant Frédéric, Hernould Michel, Chevalier Christian, Mouras Armand
Unité Mixte de Recherche 619 sur la Biologie du Fruit (Institut National de la Recherche Agronomique; Université Bordeaux 1; Université Victor Segalen-Bordeaux 2), Institut Fédératif de Recherche 103, Institut National de la Recherche Agronomique, France.
Plant J. 2007 Aug;51(4):642-55. doi: 10.1111/j.1365-313X.2007.03167.x. Epub 2007 Jun 22.
Tomato fruit size results from the combination of cell number and cell size which are respectively determined by cell division and cell expansion processes. As fruit growth is mainly sustained by cell expansion, the development of pericarp and locular tissues is characterized by the concomitant arrest of mitotic activity, inhibition of cyclin-dependent kinase (CDK) activity, and numerous rounds of endoreduplication inducing a spectacular increase in DNA ploidy and mean cell size. To decipher the molecular basis of the endoreduplication-associated cell growth in fruit, we investigated the putative involvement of the WEE1 kinase (Solly;WEE1). We here report a functional analysis of Solly;WEE1 in tomato. Impairing the expression of Solly;WEE1 in transgenic tomato plants resulted in a reduction of plant size and fruit size. In the most altered phenotypes, fruits displayed a reduced number of seeds without embryo development. The reduction of plant-, fruit- and seed size originated from a reduction in cell size which could be correlated with a decrease of the DNA ploidy levels. At the molecular level downregulating Solly;WEE1 in planta resulted in the increase of CDKA activity levels originating from a decrease of the amount of Y15-phosphorylated CDKA, thus indicating a release of the negative regulation on CDK activity exerted by WEE1. Our data indicated that Solly;WEE1 participates in the control of cell size and/or the onset of the endoreduplication process putatively driving cell expansion.
番茄果实大小是细胞数量和细胞大小共同作用的结果，而细胞数量和细胞大小分别由细胞分裂和细胞扩张过程决定。由于果实生长主要依赖于细胞扩张，果皮和心皮组织的发育特点是有丝分裂活动同时停止、细胞周期蛋白依赖性激酶（CDK）活性受到抑制以及多轮核内复制，从而导致DNA倍性和平均细胞大小显著增加。为了解析果实中与核内复制相关的细胞生长的分子基础，我们研究了WEE1激酶（Solly;WEE1）可能发挥的作用。我们在此报告了对番茄中Solly;WEE1的功能分析。在转基因番茄植株中削弱Solly;WEE1的表达会导致植株大小和果实大小减小。在变化最明显的表型中，果实的种子数量减少且无胚胎发育。植株、果实和种子大小的减小源于细胞大小的减小，这可能与DNA倍性水平的降低有关。在分子水平上，在植物体内下调Solly;WEE1会导致CDKA活性水平升高，这是由于Y15磷酸化的CDKA量减少所致，因此表明WEE1对CDK活性的负调控作用被解除。我们的数据表明，Solly;WEE1参与了对细胞大小的控制和/或可能驱动细胞扩张的核内复制过程的起始。
