DataSheet_1_Comprehensive analysis of the carboxylesterase gene reveals that NtCXE22 regulates axillary bud growth through strigolactone metabolism in tobacco.pdf

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 Nicotiana tabacum L. CXE genes (NtCXEs) were identified using a sequence homology search. The basic characteristics, phylogenetic evolution, gene structure, subcellular location, promoter cis-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.NtCXE7, NtCXE9, NtCXE22, and NtCXE24 were homologous to Arabidopsis SLs hydrolase AtCXE15, and changes in their expression levels were induced by topping and by GR24 (a synthetic analogue of strigolactone). Further examination revealed that NtCXE22-mutant (ntcxe22) plants generated by CRISPR-Cas9 technology had shorter bud outgrowth with lower SLs content. Validation of NtCXE22 was also performed in NtCCD8-OE plants (with fewer axillary buds) and in ntccd8 mutant plants (with more axillary buds). The results suggest that NtCXE22 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.

羧酸酯酶（Carboxylesterases, CXE）是一类拥有α/β折叠结构域的水解酶类，在植物生长发育、胁迫响应以及除草剂活性物质活化过程中发挥至关重要的作用。本研究通过序列同源性搜索，鉴定得到49个普通烟草（Nicotiana tabacum L.）CXE基因（命名为NtCXEs）。随后系统分析了该基因家族的基本特征、系统进化关系、基因结构、亚细胞定位、启动子顺式作用元件以及基因表达模式。RNA测序（RNA-seq）数据与实时定量PCR（quantitative real-time PCR）结果显示，CXE家族基因的表达水平与多种胁迫因子及激素密切相关；在检测的8种组织以及不同发育时期，基因表达量均存在显著差异。独脚金内酯（strigolactones, SLs）作为一类新型激素，由植物根系释放，可调控腋芽萌发。其中NtCXE7、NtCXE9、NtCXE22和NtCXE24与拟南芥独脚金内酯水解酶AtCXE15同源，它们的表达水平可被打顶处理以及GR24（一种人工合成的独脚金内酯类似物）诱导改变。进一步研究发现，通过CRISPR-Cas9技术创制的NtCXE22突变体（ntcxe22）植株腋芽生长更短，且体内独脚金内酯含量更低。本研究还在腋芽数量更少的NtCCD8过表达植株，以及腋芽数量更多的ntccd8突变体中对NtCXE22进行了功能验证。上述结果表明，NtCXE22可作为一种高效的独脚金内酯水解酶，影响腋芽发育，这为调控作物与观赏植物的内源独脚金内酯水平提供了可行的技术途径。