AUTHOR=Wang Wenbin , Qiu Xiangpo , Yang Yanxin , Kim Ho Soo , Jia Xiaoyun , Yu Huan , Kwak Sang-Soo 

TITLE=Sweetpotato bZIP Transcription Factor IbABF4 Confers Tolerance to Multiple Abiotic Stresses

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00630

DOI=10.3389/fpls.2019.00630

ISSN=1664-462X

ABSTRACT=<p>The abscisic acid (ABA)-responsive element binding factors (ABFs) play important regulatory roles in multiple abiotic stresses responses. However, information on the stress tolerance functions of <italic>ABF</italic> genes in sweetpotato (<italic>Ipomoea batatas</italic> [L.] Lam) remains limited. In the present study, we isolated and functionally characterized the sweetpotato <italic>IbABF4</italic> gene, which encodes an abiotic stress-inducible basic leucine zipper (bZIP) transcription factor. Sequence analysis showed that the IbABF4 protein contains a typical bZIP domain and five conserved Ser/Thr kinase phosphorylation sites (RXXS/T). The <italic>IbABF4</italic> gene was constitutively expressed in leaf, petiole, stem, and root, with the highest expression in storage root body. Expression of <italic>IbABF4</italic> was induced by ABA and several environmental stresses including drought, salt, and heat shock. The IbABF4 protein localized to the nucleus, exhibited transcriptional activation activity, and showed binding to the <italic>cis</italic>-acting ABA-responsive element (ABRE) <italic>in vitro</italic>. Overexpression of <italic>IbABF4</italic> in <italic>Arabidopsis thaliana</italic> not only increased ABA sensitivity but also enhanced drought and salt stress tolerance. Furthermore, transgenic sweetpotato plants (hereafter referred to as SA plants) overexpressing <italic>IbABF4</italic>, generated in this study, exhibited increased tolerance to drought, salt, and oxidative stresses on the whole plant level. This phenotype was associated with higher photosynthetic efficiency and lower malondialdehyde and hydrogen peroxide content. Levels of endogenous ABA content and ABA/stress-responsive gene expression were significantly upregulated in transgenic <italic>Arabidopsis</italic> and sweetpotato plants compared with wild-type plants under drought stress. Our results suggest that the expression of <italic>IbABF4</italic> in <italic>Arabidopsis</italic> and sweetpotato enhances tolerance to multiple abiotic stresses through the ABA signaling pathway.</p>