Ectopic expression of UGT75D1, a glycosyltransferase preferring indole-3-butyric acid, modulates cotyledon development and stress tolerance in seed germination of Arabidopsis thaliana.
The formation of auxin glucose conjugate is proposed to be one of the molecular modifications controlling auxin homeostasis. However, the involved mechanisms and relevant physiological significances are largely unknown or poorly understood. In this study, Arabidopsis UGT75D1 was at the first time identified to be an indole-3-butyric acid (IBA) preferring glycosyltransferase. Assessment of enzyme activity and IBA conjugates in transgenic plants ectopically expressing UGT75D1 indicated that the UGT75D1 catalytic specificity was maintained in planta. It was found that the expression pattern of UGT75D1 was specific in germinating seeds. Consistently, we found that transgenic seedlings with over-produced UGT75D1 exhibited smaller cotyledons and cotyledon epidermal cells than the wild type. In addition, UGT75D1 was found to be up-regulated under mannitol, salt and ABA treatments and the over-expression lines were tolerant to osmotic and salt stresses during germination, resulting in an increased germination rate. Quantitative RT-PCR analysis revealed that the mRNA levels of ABA INSENSITIVE 3 (ABI3) and ABI5 gene in ABA signaling were substantially down-regulated in the transgenic lines under stress treatments. Interestingly, AUXIN RESPONSE FACTOR 16 (ARF16) gene of transgenic lines was also dramatically down-regulated under the same stress conditions. Since ARF16 functions as an activator of ABI3 transcription, we supposed that UGT75D1 might play a role in stress tolerance during germination through modulating ARF16-ABI3 signaling. Taken together, our work indicated that, serving as the IBA preferring glycosyltransferase but distinct from other auxin glycosyltransferases identified so far, UGT75D1 might be a very important player mediating a crosstalk between cotyledon development and stress tolerance of germination at the early stage of plant growth.
Key Lab of Plant Cell Engineering and Germplasm Innovation, Chinese Ministry of Education; School of Life Sciences, Shandong University, Jinan, 250100, China.
Gui-Zhi
GZ
Zhang
School of Life Science, Qingdao Agricultural University, Qingdao, 266109, China.
Shang-Hui
SH
Jin
Key Lab of Plant Cell Engineering and Germplasm Innovation, Chinese Ministry of Education; School of Life Sciences, Shandong University, Jinan, 250100, China.
Xiao-Yi
XY
Jiang
Key Lab of Plant Cell Engineering and Germplasm Innovation, Chinese Ministry of Education; School of Life Sciences, Shandong University, Jinan, 250100, China.
Rui-Rui
RR
Dong
Key Lab of Plant Cell Engineering and Germplasm Innovation, Chinese Ministry of Education; School of Life Sciences, Shandong University, Jinan, 250100, China.
Pan
P
Li
Key Lab of Plant Cell Engineering and Germplasm Innovation, Chinese Ministry of Education; School of Life Sciences, Shandong University, Jinan, 250100, China.
Yan-Jie
YJ
Li
Key Lab of Plant Cell Engineering and Germplasm Innovation, Chinese Ministry of Education; School of Life Sciences, Shandong University, Jinan, 250100, China. bkhou@sdu.edu.cn.
Bing-Kai
BK
Hou
D000040:Abscisic Acid / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D018548:Cotyledon / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D000066630:Ectopic Gene Expression; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D018525:Germination / Q000187:drug effects; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D016695:Glycosyltransferases / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D007211:Indoles / Q000378:metabolism*; D008353:Mannitol / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000378:metabolism; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology
D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D007211:Indoles; D010937:Plant Growth Regulators; C014612:indolebutyric acid; D008353:Mannitol; D012965:Sodium Chloride; D000040:Abscisic Acid; D016695:Glycosyltransferases; D005964:Glucosyltransferases; C000607560:UGT75D1 protein, Arabidopsis
Arabidopsis thaliana; Auxins; Cotyledon; Germination; Glycosyltransferase; Stress tolerance