AUTHOR=Wang Lin , Xie Xiaodong , Xu Yalong , Li Zefeng , Xu Guoyun , Cheng Lingtong , Yang Jun , Li Lei , Pu Wenxuan , Cao Peijian 

TITLE=Comprehensive analysis of the carboxylesterase gene reveals that NtCXE22 regulates axillary bud growth through strigolactone metabolism in tobacco

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.1019538

DOI=10.3389/fpls.2022.1019538

ISSN=1664-462X

ABSTRACT=<p>Carboxylesterases (CXE) are a class of hydrolytic enzymes with α/β-folding domains that play a vital role in plant growth, development, stress response, and activation of herbicide-active substances. In this study, 49 <italic>Nicotiana tabacum</italic> L. <italic>CXE</italic> genes (NtCXEs) were identified using a sequence homology search. The basic characteristics, phylogenetic evolution, gene structure, subcellular location, promoter <italic>cis</italic>-elements, and gene expression patterns of the CXE family were systematically analyzed. RNA-seq data and quantitative real-time PCR showed that the expression level of CXEs was associated with various stressors and hormones; gene expression levels were significantly different among the eight tissues examined and at different developmental periods. As a new class of hormones, strigolactones (SLs) are released from the roots of plants and can control the germination of axillary buds.<italic>NtCXE7</italic>, <italic>NtCXE9</italic>, <italic>NtCXE22</italic>, and <italic>NtCXE24</italic> were homologous to <italic>Arabidopsis</italic> SLs hydrolase <italic>AtCXE15</italic>, and changes in their expression levels were induced by topping and by GR24 (a synthetic analogue of strigolactone). Further examination revealed that <italic>NtCXE22</italic>-mutant (<italic>ntcxe22</italic>) plants generated by CRISPR-Cas9 technology had shorter bud outgrowth with lower SLs content. Validation of <italic>NtCXE22</italic> was also performed in <italic>NtCCD8</italic>-OE plants (with fewer axillary buds) and in <italic>ntccd8</italic> mutant plants (with more axillary buds). The results suggest that <italic>NtCXE22</italic> may act as an efficient SLs hydrolase and affects axillary bud development, thereby providing a feasible method for manipulating endogenous SLs in crops and ornamental plants.</p>