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

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Bresso EG, Chorostecki U, Rodriguez RE, Palatnik JF, Schommer C