title: The tomato HD-Zip I transcription factor SlHZ24 modulates ascorbate accumulation through positive regulation of the D-mannose/L-galactose pathway.
abstract: 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, SlHZ24, binds to the promoter of an AsA biosynthetic gene encoding GDP-D-mannose pyrophosphorylase 3 (SlGMP3). Both the transient expression system and electrophoretic mobility shift assay (EMSA) showed that SlHZ24 binds to a regulatory cis-element in the SlGMP3 promoter, and further overexpression of SlHZ24 in transgenic tomato lines resulted in increased AsA levels. In contrast, suppressing expression of the gene using RNA interference (RNAi) had the opposite effect. These data suggest that SlHZ24 can positively regulate the accumulation of AsA, and in support of this it was shown that SlGMP3 expression increased in the SlHZ24-overexpressing lines and declined in SlHZ24-RNAi lines. SlHZ24 also affected the expression of other genes in the D-mannose/L-galactose pathway, such as genes encoding GDP-mannose-3',5'-epimerase 2 (SlGME2), GDP-L-galactose phosphorylase (SlGGP) and SlGMP4. The EMSA indicated that SlHZ24 bound to the promoters of SlGME2 and SlGGP, suggesting multi-targeted regulation of AsA biosynthesis. Finally, SlHZ24-overexpressing plants showed less sensitivity to oxidative stress; we therefore conclude that SlHZ24 promotes AsA biosynthesis, which in turn enhances oxidative stress tolerance.
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Tixu
authors.initials: T
authors.lastname: Hu
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Ye
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Peiwen
authors.initials: P
authors.lastname: Tao
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Hanxia
authors.initials: H
authors.lastname: Li
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Junhong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Yuyang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: The Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Zhibiao
authors.initials: Z
authors.lastname: Ye
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000096:biosynthesis* / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000235:genetics* / Q000502:physiology; D008358:Mannose / Q000378:metabolism*; D018384:Oxidative Stress; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D017382:Reactive Oxygen Species / Q000378:metabolism; D013312:Stress, Physiological; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D000975:Antioxidants; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D008358:Mannose; D001205:Ascorbic Acid; D005690:Galactose
keywords: SlGMP3; SlHZ24; ascorbate; oxidative stress; tomato