title: Expression of Brassica napus TTG2, a regulator of trichome development, increases plant sensitivity to salt stress by suppressing the expression of auxin biosynthesis genes.
abstract: WRKY transcription factors (TFs) are plant specific and play important roles in regulating diverse biological processes. To identify TFs with broad-spectrum effects on various stress responses in Brassica napus, an important oil crop grown across diverse ecological regions worldwide, we functionally characterized Bna.TTG2 genes, which are homologous to the Arabidopsis AtTTG2 (WRKY44) gene. Four Bna.TTG2 genes were capable of rescuing the trichome phenotypes of Arabidopsis ttg2 mutants. Overexpressing one Bna.TTG2 family member, BnaA.TTG2.a.1, remarkably increased trichome numbers in Arabidopsis and B. napus plants. Interestingly, the BnaA.TTG2.a.1-overexpressing plants of both species exhibited increased sensitivity to salt stress. In BnaA.TTG2.a.1-overexpressing Arabidopsis under salt stress, the endogenous indole-3-acetic acid (IAA) content was reduced, and the expression of two auxin biosynthesis genes, TRYPTOPHAN BIOSYNTHESIS 5 (TRP5) and YUCCA2 (YUC2), was downregulated. The results from yeast one-hybrid, electrophoretic mobility shift, and dual-luciferase reporter assays revealed that BnaA.TTG2.a.1 is able to bind to the promoters of TRP5 and YUC2. These data indicated that BnaA.TTG2.a.1 confers salt sensitivity to overexpressing plants by suppressing the expression of IAA synthesis genes and thus lowering IAA levels. Transgenic Arabidopsis plants with an N-terminus-deleted BnaA.TTG2.a.1 no longer showed hypersensitivity to salt stress, suggesting that the N terminus of BnaA.TTG2.a.1 plays a critical role in salt stress responses. Therefore, in addition to its classical function in trichome development, our study reveals a novel role for Bna.TTG2 genes in salt stress responses.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Li
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Yin
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Yongpeng
authors.initials: Y
authors.lastname: Li
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Chuchuan
authors.initials: C
authors.lastname: Fan
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Qingyong
authors.initials: Q
authors.lastname: Yang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Wu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon SK S7N 5A2, Canada.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China ymzhou@mail.hzau.edu.cn.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D000878:Anthranilate Synthase / Q000235:genetics* / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D029688:Brassica napus / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D064201:Trichomes / Q000187:drug effects / Q000235:genetics / Q000254:growth & development
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D014157:Transcription Factors; D012965:Sodium Chloride; D006899:Mixed Function Oxygenases; C000608861:YUCCA2 protein, Arabidopsis; C543688:ASA1 protein, Arabidopsis; D000878:Anthranilate Synthase
keywords: Arabidopsis; Bna.TTG2; Brassica napus; auxin biosynthesis; salt stress; transcription factor; trichome.