AUTHOR=Lu Zhuchou , Qiu Wenmin , Jin Kangming , Yu Miao , Han Xiaojiao , He Xiaoyang , Wu Longhua , Wu Chao , Zhuo Renyin 

TITLE=Identification and Analysis of bZIP Family Genes in Sedum plumbizincicola and Their Potential Roles in Response to Cadmium Stress

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.859386

DOI=10.3389/fpls.2022.859386

ISSN=1664-462X

ABSTRACT=<p><italic>Sedum plumbizincicola</italic> (Crassulaceae), a cadmium (Cd)/zinc (Zn)/lead (Pb) hyperaccumulator native to Southeast China, is potentially useful for the phytoremediation of heavy metal-contaminated soil. Basic leucine zipper (bZIP) transcription factors play vital roles in plant growth, development, and abiotic stress responses. However, there has been minimal research on the effects of Cd stress on the bZIP gene family in <italic>S. plumbizincicola</italic>. In this study, 92 <italic>SpbZIP</italic> genes were identified in the <italic>S. plumbizincicola</italic> genome and then classified into 12 subgroups according to their similarity to bZIP genes in <italic>Arabidopsis.</italic> Gene structure and conserved motif analyses showed that <italic>SpbZIP</italic> genes within the same subgroup shared similar intron–exon structures and motif compositions. In total, eight pairs of segmentally duplicated <italic>SpbZIP</italic> genes were identified, but there were no tandemly duplicated <italic>SpbZIP</italic> genes. Additionally, the duplicated <italic>SpbZIP</italic> genes were mainly under purifying selection pressure. Hormone-responsive, abiotic and biotic stress-responsive, and plant development-related <italic>cis</italic>-acting elements were detected in the <italic>SpbZIP</italic> promoter sequences. Expression profiles derived from RNA-seq and quantitative real-time PCR analyses indicated that the expression levels of most <italic>SpbZIP</italic> genes were upregulated under Cd stress conditions. Furthermore, a gene co-expression network analysis revealed that most edge genes regulated by hub genes were related to metal transport, responses to stimuli, and transcriptional regulation. Because its expression was significantly upregulated by Cd stress, the hub gene <italic>SpbZIP60</italic> was selected for a functional characterization to elucidate its role in the root response to Cd stress. In a transient gene expression analysis involving <italic>Nicotiana benthamiana</italic> leaves, <italic>SpbZIP60</italic> was localized in the nucleus. The overexpression of <italic>SpbZIP60</italic> enhanced the Cd tolerance of transgenic <italic>Arabidopsis</italic> plants by inhibiting ROS accumulation, protecting the photosynthetic apparatus, and decreasing the Cd content. These findings may provide insights into the potential roles of the bZIP family genes during the <italic>S. plumbizincicola</italic> response to Cd stress.</p>