AUTHOR=Habiba  , Xu Jiaxuan , Gad Ahmed G. , Luo Yuling , Fan Chunlan , Uddin Junaite Bin Gias , ul Ain Noor , Huang Chengxin , Zhang Yu , Miao Ying , Zheng Xiangzi 

TITLE=Five OsS40 Family Members Are Identified as Senescence-Related Genes in Rice by Reverse Genetics Approach

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.701529

DOI=10.3389/fpls.2021.701529

ISSN=1664-462X

ABSTRACT=<p>A total of 16 <italic>OsS40</italic> genes of <italic>Oryza sativa</italic> were identified in our previous work, but their functions remain unclear. In this study, 13 <italic>OsS40</italic> members were knocked out using the CRISPR/cas9 gene-editing technology. After screening phenotype characterization of CRISPR/Cas9 mutants compared to WT, five <italic>oss40s</italic> mutants exhibited a stay-green phenotype at 30 days after heading. Moreover, increased grain size and grain weight occurred in the <italic>oss40-1, oss40-12</italic>, and <italic>oss40-14</italic> lines, while declined grain weight appeared in the <italic>oss40-7</italic> and <italic>oss40-13</italic> mutants. The transcript levels of several senescence-associated genes (SAGs), chlorophyll degradation-related genes (CDGs), as well as WRKY members were differentially decreased in the five stay-green <italic>oss40s</italic> mutants compared to WT. Five <italic>oss40</italic> mutants also exhibited a stay-green phenotype when the detached leaves were incubated under darkness for 4 days. <italic>OsSWEET4</italic> and <italic>OsSWEET1b</italic> were significantly upregulated, while <italic>OsSWEET1a</italic> and <italic>OsSWEET13</italic> were significantly downregulated in both <italic>oss40-7</italic> and <italic>oss40-14</italic> compared to WT. Furthermore, these five <italic>OsS40</italic> displayed strong transcriptional activation activity and were located in the nucleus. Most of the <italic>OsS40</italic> genes were downregulated in the <italic>oss40-1, oss40-7</italic>, and <italic>oss40-12</italic> mutants, but upregulated in the <italic>oss40-13</italic> and <italic>oss40-14</italic> mutants, indicating coordinated regulation among <italic>OsS40</italic> members. These results suggest that <italic>OsS40-1, OsS40-7, OsS40-12, OsS40-13</italic>, and <italic>OsS40-14</italic> are senescence-associated genes, involved in the senescence and carbon allocation network by modulating other <italic>OsS40</italic> members, <italic>SWEET</italic> member genes, and senescence-related gene expression.</p>