AUTHOR=Liu Jiao , Chen Xia , Wang Shuo , Wang Yuanyuan , Ouyang Yujun , Yao Yuan , Li Ruimei , Fu Shaoping , Hu Xinwen , Guo Jianchun 

TITLE=MeABL5, an ABA Insensitive 5-Like Basic Leucine Zipper Transcription Factor, Positively Regulates MeCWINV3 in Cassava (Manihot esculenta Crantz)

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00772

DOI=10.3389/fpls.2019.00772

ISSN=1664-462X

ABSTRACT=<p>The basic leucine zipper (bZIP) transcription factor family plays crucial roles in multiple biological processes, especially stress responses. Cassava (<italic>Manihot esculenta</italic> Crantz) is an important tropical crop with a strong tolerance to environmental stresses such as drought, heat, and low-fertility environments. Currently, limited information is available regarding the functional identification of bZIP transcription factors in response to abiotic stress in cassava. Herein, a gene encoding an ABA Insensitive 5 (ABI5)-like transcription factor, designated as <italic>MeABL5</italic>, was identified in cassava. Sequence and phylogenetic analysis showed that MeABL5 is a cassava bZIP transcription factor that is not included in the previously identified cassava bZIP family members, belongs to subfamily A, and has high sequence similarity to ABI5-like proteins. Subcellular localization and transactivation assays revealed that MeABL5 was a nuclear-localized protein and possessed transactivation activity. Furthermore, MeABL5 was able to specifically interact with the ABRE cis-element in the promoter of the cassava major cell wall invertase gene, <italic>MeCWINV3, in vitro</italic> and <italic>in vivo. MeABL5</italic> and <italic>MeCWINV3</italic> exhibited similar expression patterns in various organs or tissues and under abiotic stress in cassava. The expressions of <italic>MeABL5</italic> and <italic>MeCWINV3</italic> within cassava plantlets were both induced by exogenous abscisic acid (ABA), gibberellic acid (GA3), methyl jasmonate (MeJA), and heat. Overexpression of <italic>MeABL5</italic> increased the activity of the <italic>MeCWINV3</italic> gene, and the up-regulated expressions of <italic>MeCWINV3</italic> were significantly activated under ABA-, salicylic acid (SA)-, and MeJA-induced conditions. Overall, these results suggest that <italic>MeABL5</italic> is a positive regulator of <italic>MeCWINV3</italic> and might participate in the robust resistance of cassava in response to abiotic stress. This study also provides a foundation for further research on ABA-mediated and stress-related signaling pathways in cassava.</p>