AUTHOR=Wang Bo , Du Hong , Zhang Zhennan , Xu Wenzhong , Deng Xin 

TITLE=BhbZIP60 from Resurrection Plant Boea hygrometrica Is an mRNA Splicing-Activated Endoplasmic Reticulum Stress Regulator Involved in Drought Tolerance

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.00245

DOI=10.3389/fpls.2017.00245

ISSN=1664-462X

ABSTRACT=<p>Adverse environmental conditions cause endoplasmic reticulum (ER) stress in plants. To mitigate ER stress damage, ER associated transcription factors and inositol-requiring enzyme-1 (IRE1)-mediated <italic>bZIP60</italic> mRNA splicing are activated in plants. A drought-induced gene, encoding the ortholog of AtbZIP60, was identified in the resurrection plant <italic>Boea hygrometrica</italic>, termed <italic>BhbZIP60</italic>. In response to ER stress and dehydration, <italic>BhbZIP60</italic> mRNA can be spliced to create a frame shift in the C terminus by the excision of 23b segment in a manner of its ortholog in other plants, thus translocating to the nucleus instead of the cytoplasm. The splicing-activated BhbZIP60 (BhbZIP60S) could function in the same way as its <italic>Arabidopsis</italic> ortholog by restoring the molecular phenotype of the mutant <italic>atbzip60</italic>. When overexpressed in <italic>Arabidopsis, BhbZIP60S</italic> provided transgenic plants with enhanced tolerance to drought, tunicamycin and mannitol stresses with upregulation of the expressions of ER quality control (QC) genes (<italic>BiP2, BiP3, CNX1</italic>, and <italic>sPDI</italic>) and abscisic acid (ABA) responsive genes (<italic>RD29A, RAB18</italic>, and <italic>RD17</italic>). Furthermore, in the yeast one-hybrid system, BhbZIP60S was capable of interacting with ER stress responsive elements (ERSE and ERSE-II) that exist in the promoters of known ER-QC genes, but not binding to ABA responsive <italic>cis</italic>-elements (ABREs). Our results demonstrated that drought-induced BhbZIP60 may have a function in drought tolerance via the splicing-activated BhbZIP60S to mediate ER-QC by direct binding to the promoters of ER-QC genes. This study evidently demonstrates the involvement of ER-QC in the drought tolerance of <italic>Arabidopsis</italic> and the desiccation tolerance of the resurrection plant <italic>B. hygrometrica</italic>.</p>