Table_2_Genome-wide identification of XTH genes in Liriodendron chinense and functional characterization of LcXTH21.xlsx

Liriodendron chinense is a relic tree species of the family Magnoliaceae with multiple uses in timber production, landscape decoration, and afforestation. L. chinense often experiences drought stress in arid areas. However, the molecular basis underlying the drought response of L. chinense remains unclear. Many studies have reported that the xyloglucan endotransglucosylase/hydrolase (XTH) family plays an important role in drought stress resistance. Hereby, to explore the drought resistance mechanism of L. chinense, we identify XTH genes on a genome-wide scale in L. chinense. A total of 27 XTH genes were identified in L. chinense, and these genes were classified into three subfamilies. Drought treatment and RT-qPCR analysis revealed that six LcXTH genes significantly responded to drought stress, especially LcXTH21. Hence, we cloned the LcXTH21 gene and overexpressed it in tobacco via gene transfer to analyze its function. The roots of transgenic plants were more developed than those of wild-type plants under different polyethylene glycol (PEG) concentration, and further RT-qPCR analysis showed that LcXTH21 highly expressed in root compared to aboveground organs, indicating that LcXTH21 may play a role in drought resistance through promoting root development. The results of this study provide new insights into the roles of LcXTH genes in the drought stress response. Our findings will also aid future studies of the molecular mechanisms by which LcXTH genes contribute to the drought response.

鹅掌楸（Liriodendron chinense）是木兰科的孑遗树种，兼具木材生产、景观美化与造林等多重用途。该物种在干旱地区常遭受干旱胁迫，但其响应干旱胁迫的分子基础仍未明确。诸多研究表明，木葡聚糖内转糖苷酶/水解酶（xyloglucan endotransglucosylase/hydrolase，XTH）家族在干旱胁迫抗性中发挥关键作用。为解析鹅掌楸的抗旱机制，本研究在全基因组范围内对鹅掌楸的XTH基因家族开展鉴定工作，最终在鹅掌楸中鉴定得到27个XTH基因，可划分为3个亚家族。通过干旱处理与实时荧光定量PCR（RT-qPCR）分析发现，6个LcXTH基因可显著响应干旱胁迫，其中以LcXTH21的响应尤为突出。随后，我们克隆获得LcXTH21基因，并通过基因转化手段将其在烟草中过表达以解析其功能。在不同浓度聚乙二醇（polyethylene glycol，PEG）胁迫处理下，转基因植株的根系发育状况优于野生型植株；进一步的RT-qPCR分析显示，相较于地上组织，LcXTH21在根系中呈高表达模式，表明LcXTH21可能通过促进根系发育参与鹅掌楸的抗旱过程。本研究结果为鹅掌楸LcXTH基因家族在干旱胁迫响应中的作用提供了新的研究视角，其研究发现也将为后续解析LcXTH基因参与干旱响应的分子机制提供重要参考。