ATHB4 and HAT3, two class II HD-ZIP transcription factors, control leaf development in Arabidopsis

• DOI: 10.4161/psb.21824
• Publication Date: 2012-10-26T20:56:30Z
• Authors: Jordi Bou-Torrent; Mercè Salla-Martret; Ronny Brandt; Thomas Musielak; Jean-Christophe P...; Jaime F. Martínez...; Stephan Wenkel
• Keywords: Homeodomain Proteins; 0303 health sciences; Arabidopsis Proteins; [SDV]Life Sciences [q-bio]; Short Communication; Arabidopsis; Cotyledon/genetics/growth & development/metabolism; Plants; 15. Life on land; Transcription Factors/genetics/ metabolism; Plants, Genetically Modified; Homeodomain Proteins/genetics/ metabolism; Plant Leaves; 03 medical and health sciences; Gene Expression Regulation; Plant Leaves/genetics/ growth & development/ metabolism; Arabidopsis Proteins/genetics/ metabolism; Gene Expression Regulation, Plant; Plant/genetics/physiology; Arabidopsis/genetics/ growth & development/ metabolism; Cotyledon; Genetically Modified/genetics/growth & development/metabolism; Transcription Factors

In response to plant proximity or canopy shade, plants can react by altering elongation growth and development. Several members of the class II homeodomain-leucine zipper (HD-ZIPII) transcription factor family have been shown to play an instrumental role in the responses to shade. HD-ZIP members of the class III (HD-ZIPIII), by contrast, are involved in basic patterning processes. We recently showed that REVOLUTA (REV), a member of the HD-ZIPIII family, directly and positively regulates the expression of several genes involved in shade-induced growth, such as those encoding HD-ZIPII factors HAT2, HAT3, ATHB2/HAT4 and ATHB4, and of the components of the auxin biosynthesis pathway YUCCA5 and TAA1. Furthermore, we could demonstrate a novel role for HD-ZIPIII in shade-induced promotion of growth. Here we show that besides responding to shade, ATHB4 and HAT3 have a critical role in establishing the dorso-ventral axis in cotyledons and developing leaves. Loss-of-function mutations in these two HD-ZIPII genes (athb4 hat3) results in severely abaxialized, entirely radialized leaves. Conversely, overexpression of HAT3 results in adaxialized leaf development. Taken together, our findings unravel a so far unappreciated role for an HD-ZIPII/HD-ZIPIII module required for dorso-ventral patterning of leaves. The finding that HD-ZIPII/HD-ZIPIII also function in shade avoidance suggests that this module is at the nexus of patterning and growth promotion.