Negative Feedback Regulation of Auxin Signaling by ATHB8/ACL5-BUD2 Transcription Module

作     者：Simona Baima Valentina Forte Marco Possenti Andres Penalosa Guido Leoni Sergio Salvi Barbara Felici Ida Ruberti Giorgio Morelli 

作者机构：Food and Nutrition Research Centre Agricultural Research Council Via Ardeatina 546 00178 Rome Italy Present address: Department of Physics Sapienza University of Rome Rle A Moro 5 00185 Rome Italy Present address: Soil-Plant System Studies Research Centre Agricultural Research Council Via della Navicella 2-4 00184 Rome Italy Institute of Biology Molecular Medicine and NanoBiotechnology National Research Council Rle A. Moro 5 00185 Rome Italy 

出 版 物：《Molecular Plant》 (分子植物（英文版）)

年 卷 期：2014年第7卷第6期

页      面：1006-1025页

核心收录：

学科分类：0710[理学-生物学] 071001[理学-植物学] 07[理学] 0901[农学-作物学] 0902[农学-园艺学] 071002[理学-动物学] 

基　　金：the Ministry for Education, University and Research, FIRBERA-PG Program the Ministry for the Agricultural, Food and Forestry Policies, AGRONANOTECH and NUTRIGEA Programs the Italian Ministry of Economy and Finance, FaReBio di Qualita Project 

主　　题：auxin procambium thermospermine autoregulation auxin influx transporters Arabidopsis. 

摘      要：The role of auxin as main regulator of vascular differentiation is well established, and a direct correlation between the rate of xylem differentiation and the amount of auxin reaching the （pro）cambial cells has been proposed. It has been suggested that thermospermine produced by ACAULIS5 （ACL5） and BUSHY AND DWARF2 （BUD2） is one of the factors downstream to auxin contributing to the regulation of this process in Arabidopsis. Here, we provide an in-depth characterization of the mechanism through which ACL5 modulates xylem differentiation. We show that an increased level of ACL5 slows down xylem differentiation by negatively affecting the expression of homeodomain-leucine zipper （HD- ZIP） III and key auxin signaling genes. This mechanism involves the positive regulation of thermospermine biosynthesis by the HD-ZIP III protein ARABIDOPSIS THALIANA HOMEOBOX8 tightly controlling the expression of ACL5 and BUD2. In addition, we show that the HD-ZIP III protein REVOLUTA contributes to the increased leaf vascularization and long hypocotyl phenotype of acl5 likely by a direct regulation of auxin signaling genes such as LIKE AUXIN RESISTANT2 （LAX2） and LAX3. We propose that proper formation and differentiation of xylem depend on a balance between positive and negative feedback loops operating through HD-ZIP III genes.