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The transcription factor Fc WRKY 40 of Fortunella crassifolia functions positively in salt tolerance through modulation of ion homeostasis and proline biosynthesis by directly regulating SOS 2 and P5 CS 1 homologs
Author(s) -
Dai Wenshan,
Wang Min,
Gong Xiaoqing,
Liu JiHong
Publication year - 2018
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.15240
Subject(s) - proline , transgene , wrky protein domain , gene silencing , transcription factor , biology , microbiology and biotechnology , biochemistry , chemistry , gene , mutant , arabidopsis , amino acid
Summary Although some WRKY s have been characterized, regulatory roles of most WRKY s remain poorly understood. Herein, we elucidated function of Fc WRKY 40 from Fortunella crassifolia in salt tolerance via overexpression and virus‐induced gene silencing ( VIGS ) and unraveled its target genes. Overexpression of Fc WRKY 40 enhanced salt tolerance in transgenic tobacco and lemon, while silencing of Fc WRKY 40 increased salt susceptibility. Homolog genes of Salt Overly Sensitive 2 ( SOS 2 ) and Δ‐1‐pyrroline‐5‐carboxylate synthetase 1 ( P5 CS 1 ) were dramatically up‐regulated in transgenic lemon but down‐regulated in VIGS line. Consistently, transgenic lemon displayed lower Na + and higher proline concentrations, whereas the silenced line accumulated more Na + but less proline. Treatment of transgenic lemon with 24‐ epi ‐brassinolide compromised salt tolerance, while supply of exogenous proline partially restored salt tolerance of the VIGS line. Fc WRKY 40 specifically binds to and activates promoters of Fc SOS 2 and FcP5 CS 1 . Fc WRKY 40 was up‐regulated by ABA and salt, and confirmed as a target of ABA ‐responsive element binding factor 2 (Fc ABF 2). Moreover, salt treatment up‐regulated Fc ABF 2 and FcP5 CS 1 , and elevated proline concentrations. Taken together, our findings demonstrate that Fc WRKY 40 participates in the ABA signaling pathway and as a positive regulator functions in salt tolerance by regulating genes involved in ion homeostasis and proline biosynthesis.