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The tomato HD ‐Zip I transcription factor Sl HZ 24 modulates ascorbate accumulation through positive regulation of the d ‐mannose/ l ‐galactose pathway
Author(s) -
Hu Tixu,
Ye Jie,
Tao Peiwen,
Li Hanxia,
Zhang Junhong,
Zhang Yuyang,
Ye Zhibiao
Publication year - 2016
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.13085
Subject(s) - electrophoretic mobility shift assay , rna interference , transcription factor , promoter , mannose , biochemistry , repressor , reactive oxygen species , gene , gene expression , microbiology and biotechnology , oxidative stress , biology , chemistry , rna
Summary Ascorbate (AsA) is an antioxidant that can scavenge the reactive oxygen species ( ROS ) produced when plants encounter stressful conditions. Here, it was revealed by a yeast one‐hybrid assay that a tomato ( Solanum lycopersicum ) HD ‐Zip I family transcription factor, Sl HZ 24, binds to the promoter of an AsA biosynthetic gene encoding GDP ‐ d ‐mannose pyrophosphorylase 3 ( Sl GMP 3 ). Both the transient expression system and electrophoretic mobility shift assay ( EMSA ) showed that Sl HZ 24 binds to a regulatory cis ‐element in the Sl GMP 3 promoter, and further overexpression of Sl HZ 24 in transgenic tomato lines resulted in increased AsA levels. In contrast, suppressing expression of the gene using RNA interference ( RNA i) had the opposite effect. These data suggest that Sl HZ 24 can positively regulate the accumulation of AsA, and in support of this it was shown that Sl GMP 3 expression increased in the Sl HZ 24 ‐overexpressing lines and declined in Sl HZ 24 ‐ RNA i lines. Sl HZ 24 also affected the expression of other genes in the d ‐mannose/ l ‐galactose pathway, such as genes encoding GDP ‐mannose‐3′,5′‐epimerase 2 (Sl GME 2), GDP ‐ l ‐galactose phosphorylase (Sl GGP ) and Sl GMP 4. The EMSA indicated that Sl HZ 24 bound to the promoters of Sl GME 2 and Sl GGP , suggesting multi‐targeted regulation of AsA biosynthesis. Finally, Sl HZ 24 ‐overexpressing plants showed less sensitivity to oxidative stress; we therefore conclude that Sl HZ 24 promotes AsA biosynthesis, which in turn enhances oxidative stress tolerance.