Transcriptome analysis reveals regulatory mechanisms of different drought-tolerant Gleditsia sinensis seedlings under drought stress.

Background: Gleditsia sinensis is a significant tree species from both ecological and economic perspectives. However, its growth is hampered by temporary droughts during the seedling stage, thereby impeding the development of the G. sinensis industry. Drought stress and rehydration of semi-annual potted seedlings using an artificial simulated water control method. RNA sequencing (RNA-seq) analyses were conducted on leaves collected from highly resistant (HR) and highly susceptible (HS) seedling families at five different stages during the process of drought stress and rehydration to investigate their gene expression patterns.

Results: The differentially expressed genes (DEGs) were predominantly enriched in pathways related to "chloroplast" (GO:0009507), "photosynthesis" (GO:0015979), "plant hormone signal transduction" (map04075), "flavonoid biosynthesis" (map00941), "stress response", "response to reactive oxygen species (ROS)" (GO:0000302), "signal transduction" (GO:0007165) in G. sinensis HR and HS families exposed to mild and severe drought stress. Additionally, the pathways related to "plant hormone signal transduction" (map04075), and osmoregulation were also enriched. The difference in drought tolerance between the two families of G. sinensis may be associated with "transmembrane transporter activity" (GO:0022857), "stress response", "hormones and signal transduction" (GO:0007165), "cutin, suberine and wax biosynthesis" (map00073), "ribosome" (map03010), "photosynthesis" (map00195), "sugar metabolism", and others. An enrichment analysis of DEGs under severe drought stress suggests that the drought tolerance of both families may be related to "water-soluble vitamin metabolic process" (GO:0006767), "photosynthesis" (map00195), "plant hormone signal transduction" (map04075), "starch and sucrose metabolism" (map00500), and "galactose metabolism" (map00052). Osmoregulation-related genes such as delta-1-pyrroline-5-carboxylate synthase (P5CS), Amino acid permease (AAP), Amino acid permease 2 (AAP2) and Trehalose-phosphate synthase (TPS), as well as the antioxidant enzyme L-ascorbate peroxidase 6 (APX6), may be significant genes involved in drought tolerance in G. sinensis. Five genes were selected randomly to validate the RNA-seq results using quantitative real-time PCR (RT-qPCR) and they indicated that the transcriptome data were reliable.

Conclusions: The study presents information on the molecular regulation of the drought tolerance mechanism in G. sinensis and provides a reference for further research on the molecular mechanisms involved in drought tolerance breeding of G. sinensis.