AUTHOR=Peng Jianling , Berbel Ana , Madueño Francisco , Chen Rujin 

TITLE=AUXIN RESPONSE FACTOR3 Regulates Compound Leaf Patterning by Directly Repressing PALMATE-LIKE PENTAFOLIATA1 Expression in Medicago truncatula

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01630

DOI=10.3389/fpls.2017.01630

ISSN=1664-462X

ABSTRACT=<p>Diverse leaf forms can be seen in nature. In <italic>Medicago truncatula, PALM1</italic> encoding a Cys(2)His(2) transcription factor is a key regulator of compound leaf patterning. PALM1 negatively regulates expression of <italic>SGL1</italic>, a key regulator of lateral leaflet initiation. However, how <italic>PALM1</italic> itself is regulated is not yet known. To answer this question, we used promoter sequence analysis, yeast one-hybrid tests, quantitative transcription activity assays, ChIP-PCR analysis, and phenotypic analyses of overexpression lines and mutant plants. The results show that <italic>M. truncatula</italic> AUXIN RESPONSE FACTOR3 (MtARF3) functions as a direct transcriptional repressor of <italic>PALM1</italic>. MtARF3 physically binds to the <italic>PALM1</italic> promoter sequence in yeast cells. MtARF3 selectively interacts with specific auxin response elements (AuxREs) in the <italic>PALM1</italic> promoter to repress reporter gene expression in tobacco leaves and binds to specific sequences in the <italic>PALM1</italic> promoter <italic>in vivo</italic>. Upregulation of <italic>MtARF3</italic> or removal of both <italic>PHANTASTICA</italic> (<italic>PHAN</italic>) and <italic>ARGONAUTE7</italic> (<italic>AGO7</italic>) pathways resulted in compound leaves with five narrow leaflets arranged in a palmate-like configuration. These results support that MtARF3, in addition as an adaxial-abaxial polarity regulator, functions to restrict spatiotemporal expression of <italic>PALM1</italic>, linking auxin signaling to compound leaf patterning in the legume plant <italic>M. truncatula.</italic></p>