MYB308-mediated transcriptional activation of plasma membrane H+-ATPase 6 promotes iron uptake in citrus

Author:

Fan Zhengyan1,Wu Yifang1,Zhao Liuying1,Fu Lina1,Deng Lile1,Deng Jiarui2,Ding Dekuan2,Xiao Shunyuan3,Deng Xiuxin1,Peng Shu’ang1,Pan Zhiyong1

Affiliation:

1. Huazhong Agricultural University Key Laboratory of Horticultural Plant Biology (Ministry of Education), Key Laboratory of Horticultural Crop Biology and Genetic Improvement (Central Region, Ministry of Agriculture), College of Horticulture and Forestry Sciences, , Wuhan 430070, China

2. Chenggu Fruit Industry Technical Guidance Station , Shaanxi 723200, China

3. University of Maryland College Park Institute for Bioscience and Biotechnology Research & Department of Plant Sciences and Landscape Architecture, , Rockville, MD 20850, USA

Abstract

Abstract Iron-deficiency chlorosis is a common nutritional disorder in crops grown on alkaline or calcareous soils. Although the acclimation mechanism to iron deficiency has been investigated, the genetic regulation of iron acquisition is still unclear. Here, by comparing the iron uptake process between the iron-poor-soil-tolerant citrus species Zhique (ZQ) and the iron-poor-soil-sensitive citrus species trifoliate orange (TO), we discovered that enhanced root H + efflux is crucial for the tolerance to iron deficiency in ZQ. The H+ efflux is mainly regulated by a plasma membrane-localized H+-ATPase, HA6, the expression of which is upregulated in plants grown in soil with low iron content, and significantly higher in the roots of ZQ than TO. Overexpression of the HA6 gene in the Arabidopsis thaliana aha2 mutant, defective in iron uptake, recovered the wild-type phenotype. In parallel, overexpression of the HA6 gene in TO significantly increased iron content of plants. Moreover, an iron deficiency-induced transcription factor, MYB308, was revealed to bind the promoter and activate the expression of HA6 in ZQ in yeast one-hybrid, electrophoretic mobility shift, and dual-luciferase assays. Overexpression of MYB308 in ZQ roots significantly increased the expression level of the HA6 gene. However, MYB308 cannot bind or activate the HA6 promoter in TO due to the sequence variation of the corresponding MYB308 binding motif. Taking these results together, we propose that the MYB308 could activate HA6 to promote root H+ efflux and iron uptake, and that the distinctive MYB308-HA6 transcriptional module may be, at least in part, responsible for the iron deficiency tolerance in citrus.

Publisher

Oxford University Press (OUP)

Subject

Horticulture,Plant Science,Genetics,Biochemistry,Biotechnology

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