Spatial control of gene expression by miR319-regulated TCP transcription factors in leaf development

The characteristic leaf shapes we see in all plants are in good part outcome of the combined action of several transcription factor networks that translate into cell division activity during the early development of the organ. We show here that wild-type leaves have distinct transcriptomic profiles in center and marginal regions. Certain transcripts are enriched in margins, including those of CINCINNATA-like TCPs, and members of the NGATHA (NGA) and STYLISH (STY) gene families. We study in detail the contribution of miR319 regulated TCP (Teosinte branched, Cycloidea, PCF1/2) transcription factors to the development of the center and marginal regions of Arabidopsis leaves. We compare in molecular analyses wildtype, a tcp2 tcp4 mutant that has enlarged flat leaves and a tcp2 tcp3 tcp4 tcp10 mutant with strongly crinkled leaves. The different leaf domains of the tcp mutants show changed expression patterns for many photosynthesis related genes, indicating delayed differentiation, especially in the marginal parts of the organ. At the same time, we found an upregulation of cyclin genes and other genes that are known to participate in cell division, specifically in the marginal regions of tcp2 tcp3 tcp4 tcp10. Using GUS reporter constructs we confirmed extended mitotic activity in the tcp2 tcp3 tcp4 tcp10 leaf which persisted in small defined foci in the margins when the mitotic activity had already ceased in wild-type leaves. Our results describe the role of miR319-regulated TCP transcription factors in the coordination of activities in different leaf domains during the organs development. Overall design: Examination of gene expression of two portions of leaves of different TCP transcription factors mutant lines

我们在所有植物中观察到的典型叶形，在很大程度上由若干转录因子网络（transcription factor networks）协同作用塑造——这些网络可调控器官早期发育阶段的细胞分裂活性。本研究证实，野生型叶片的中心区域与边缘区域存在显著差异的转录组谱（transcriptomic profiles）。部分转录本在叶片边缘区域富集，其中包括类CINCINNATA的TCP（Teosinte branched, Cycloidea, PCF1/2）转录因子，以及NGATHA（NGA）、STYLISH（STY）基因家族的成员。我们详细探究了受miR319调控的TCP（Teosinte branched, Cycloidea, PCF1/2）转录因子对拟南芥叶片中心与边缘区域发育的调控作用。本研究通过分子分析，对比了野生型、携带平展增大叶片的tcp2 tcp4突变体，以及叶片严重皱缩的tcp2 tcp3 tcp4 tcp10四突变体。上述tcp突变体的不同叶片区域中，诸多光合作用相关基因的表达模式发生改变，提示细胞分化过程出现延迟，尤以叶片边缘区域更为显著。与此同时，我们发现在tcp2 tcp3 tcp4 tcp10四突变体的叶片边缘区域，细胞周期蛋白基因及其他已知参与细胞分裂的基因呈现上调表达。我们借助GUS报告基因载体（GUS reporter constructs）证实，tcp2 tcp3 tcp4 tcp10四突变体叶片的有丝分裂活性持续时间延长：当野生型叶片的有丝分裂活性已完全终止时，该突变体叶片边缘仍存在少量明确的细胞集落，持续维持有丝分裂活性。本研究结果阐明了受miR319调控的TCP转录因子在植物器官发育过程中，协调不同叶片区域生理活动的核心功能。实验整体设计：对不同TCP转录因子突变体株系的叶片两部分区域开展基因表达检测。