Abstract
Leaves grow by distinct phases controlled by gene regulatory networks including many transcription factors. Arabidopsis thaliana homeobox 12 (ATHB12) promotes leaf growth especially during the cell expansion phase. In this study, we identify TCP13, a member of the TCP transcription factor family, as an upstream inhibitor of ATHB12. Yeast one-hybrid screening using a 1.2-kb upstream region of ATHB12 resulted in the isolation of TCP13 as well as other transcription factors. Transgenic plants constitutively expressing TCP13 displays a significant reduction in leaf cell size especially during the cell expansion period, while repression of TCP13 and its paralogs (TCP5 and TCP17) result in enlarged leaf cells, indicating that TCP13 and its paralogs inhibit leaf development, mainly at the cell expansion phase. Its expression pattern during leaf expansion phase is opposite to ATHB12 expression. Consistently, the expression of ATHB12 and its downstream genes decreases when TCP13 was overexpressed, and increases when the expression of TCP13 and its paralogs is repressed. In chromatin immunoprecipitation assays using TCP13-GFP plants, a fragment of the ATHB12 upstream region that contains the consensus sequence for TCP binding is strongly enriched. Taken together, these findings indicate that TCP13 and its paralogs inhibit leaf growth by repressing ATHB12 expression.
Highlights
Leaves are plant organs essential for harvesting the light that provides energy for living organisms
Arabidopsis thaliana homeobox 12 (ATHB12) upstream region that contains the consensus sequence for TCP binding is strongly enriched. These findings indicate that TCP13 and its paralogs inhibit leaf growth by repressing
We examined the effect of Arabidopsis thaliana homeobox 2 (ATHB2) on the expression of ATHB12 because TCP13 was found to interact with ATHB2 and ATHB2 contains an EAR motif, a well-known transcriptional repression motif in plants [41]
Summary
Leaves are plant organs essential for harvesting the light that provides energy for living organisms. The development of leaves involves complicated coordination of several factors including correct spatio-temporal transcriptional regulation of genes, hormonal control, and responses to environmental conditions [1,2,3,4,5]. While cell division continues at the base of the leaf, cell expansion starts at the tip and moves to the base, forming the cell cycle arrest front [1,6,7]. Differentiation occurs to form specialized cells such as guard cells. Homeobox genes affect plant development as well as the development of various animals [8,9]
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