Genome-wide identification and characterization of the GDSL lipase gene family in Dendrobium catenatum and their potential role in drought stress tolerance and stomatal outer cuticular ledge formation

Jing Tang¹Jiaying Li²Chunyan Tang¹Xingyu Han¹Haiying Zhang¹Beiqi Yang¹Long Xiao³Ruiying Li⁴Hangxing Liu³Dengjin Pi³Qinsong Liu³Disha Hu³Ke Tian¹Youfa Li¹Qian Wang¹Lin Qin^3*

• ¹Key Laboratory of Oral Disease Research of Guizhou Provincial Department of Education, School of Stomatology, Zunyi Medical University, Zunyi, China
• ²Academy of Biomedical Engineering, Kunming Medical University, Kunming, China
• ³Guizhou Engineering Research Center of Industrial Key-technology for Dendrobium Nobile, Zunyi Medical University, Zunyi, China
• ⁴National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China

Background: Dendrobium catenatum, a drought-resistant medicinal orchid, exhibits unique adaptations to arid environments; however, the underlying molecular mechanisms remain largely unknow. The formation of the abnormal stomatal outer cuticular ledge (OCL) is prevalent in D. catenatum and is thought to contribute to its drought tolerance. Despite this, the GDSL lipases that regulate drought resistance in D. catenatum have not yet been identified. This study aimed to systematically identify the GDSL lipase family in D. catenatum, analyze their expression patterns, screen for candidates highly expressed in the leaf epidermis and stomatal guard cells, and validate their roles through drought tolerance assays and stomatal OCL characterization. Methods: A total of 58 GDSL lipase genes were identified from the D. catenatum genome. Nine endoplasmic reticulum-localized, drought-responsive candidates were selected for functional characterization in Arabidopsis. Results: Overexpression of D. catenatum GDSL (DcaGDSL) 25, 39, 47, and 52 in Arabidopsis decreased drought tolerance, with DcaGDSL47-overexpressing lines exhibiting accelerated water loss. Notably, DcaGDSL47, which is enriched in stomatal, reduced drought tolerance, accelerated stomatal water loss, and caused the degradation of stomatal OCL when overexpressed in Arabidopsis. These findings suggest that DcaGDSL47 plays a key role in regulating stomatal OCL formation and drought adaptation. Conclusion: This study highlights the essential roles of GDSL lipases in modulating stomatal OCL formation and drought adaptation in D. catenatum, providing a molecular basis for further investigation of drought resistance mechanisms from the perspective of stomatal OCL formation.