Multiple mechanisms explain how reduced KRP expression increases leaf size of Arabidopsis thaliana

First author: Bulelani L. Sizani; Affiliations: University of Antwerp (安特卫普大学): Antwerp, Belgium

Corresponding author: Gerrit T. S. Beemster

Although cell number generally correlates with organ size, the role of cell cycle control in growth regulation is still largely unsolved. We studied kip related protein (krp) 4, 6 and 7 single, double and triple mutants of Arabidopsis thaliana to understand the role of cell cycle inhibitory proteins in leaf development. We performed leaf growth and seed size analysis, kinematic analysis (动力分析), flow cytometery, transcriptome analysis and mathematical modeling of G1/S and G2/M checkpoint progression of the mitotic and endoreplication cycle. Double and triple mutants progressively increased mature leaf size, because of elevated expression of cell cycle and DNA replication genes stimulating progression through the division and endoreplication cycle. However, cell number was also already increased before leaf emergence, as a result of an increased cell number in the embryo. We show that increased embryo and seed size in krp4/6/7 results from seed abortion, presumably reducing resource competition, and that seed size differences contribute to the phenotype of several large‐leaf mutants. Our results provide a new mechanistic understanding of the role of cell cycle regulation in leaf development and highlight the contribution of the embryo to the development of leaves after germination in general.

尽管细胞数量正常与器官的大小呈比例关系，但细胞周期在生长调控中的作用还不是很清楚。本文中，作者通过拟南芥kip相关蛋白krp4、krp6和krp7的单突、双突及三突研究细胞周期抑制蛋白在叶片发育中的作用。作者进行了叶片生长、种子大小的分析、细胞动力学分析、流式细胞术及转录组分析，并且对有丝分裂和内复制周期的G1/S和G2/M两个细胞周期连续过渡时期进行了数学建模。双突和三突植株的细胞周期和DNA复制基因表达的降低，进而通过细胞分裂的内复制循环逐步增加了成熟叶片的大小。然而，由于在胚胎时期的细胞数量增加，因此在叶片形成之前细胞的数量也增加了。进一步的研究显示krp4/6/7中胚胎和种子大小的增加是由于种子败育所导致的，这可能减少了资源的竞争，并且种子大小的差异作用于一些具有较大叶片突变体的表型。本文的研究表明了细胞周期在叶片发育中的调控作用，并且揭示了胚胎对于萌发后叶片发育的作用。

doi: https://doi.org/10.1111/nph.15458

Journal: New Phytologist

First Published: 29 September, 2018

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