Transcriptomic responses to drought stress in Polygonatum kingianum tuber

Abstract

Background Polygonatum kingianum Coll. et Hemsl. is an important plant in Traditional Chinese Medicine. The extracts from its tubers are rich in polysaccharides and other metabolites such as saponins. It is a well-known concept that growing medicinal plants in semi-arid (or drought stress) increases their natural compounds concentrations. This study was conducted to explore the morpho-physiological responses of P. kingianum plants and transcriptomic signatures of P. kingianum tubers exposed to mild, moderate, and severe drought and rewatering. Results The stress effects on the morpho-physiological parameters were dependent on the intensity of the drought stress. The leaf area, relative water content, chlorophyll content, and shoot fresh weight decreased whereas electrolyte leakage increased with increase in drought stress intensity. A total of 53,081 unigenes were obtained; 59% of which were annotated. We observed that 1352 and 350 core genes were differentially expressed in drought and rewatering, respectively. Drought stress driven differentially expressed genes (DEGs) were enriched in phenylpropanoid biosynthesis, flavonoid biosynthesis, starch and sucrose metabolism, and stilbenoid diarylheptanoid and gingerol biosynthesis, and carotenoid biosynthesis pathways. Pathways such as plant-pathogen interaction and galactose metabolism were differentially regulated between severe drought and rewatering. Drought reduced the expression of lignin, gingerol, and flavonoid biosynthesis related genes and rewatering recovered the tubers from stress by increasing the expression of the genes. Increased expression of carotenoid biosynthesis pathway related genes under drought suggested their important role in stress endurance. An increase in starch and sucrose biosynthesis was evident from transcriptomic changes under drought stress. Rewatering recovered the drought affected tubers as evident from the contrasting expression profiles of genes related to these pathways. P. kingianum tuber experiences an increased biosynthesis of sucrose, starch, and carotenoid under drought stress. Drought decreases the flavonoids, phenylpropanoids, gingerol, and lignin biosynthesis. These changes can be reversed by rewatering the P. kingianum plants. Conclusions These results provide a transcriptome resource for P. kingianum and expands the knowledge on the effect of drought and rewatering on important pathways. This study also provides a large number of candidate genes that could be manipulated for drought stress tolerance and managing the polysaccharide and secondary metabolites’ contents in P. kingianum.

Transcriptome Profiling of Gossypium anomalum Seedlings Reveals Key Regulators and Metabolic Pathways in Response to Drought Stress

“…These DEGs exhibited significant enrichments for molecular functions GO terms related to cytoskeleton, hydrolase activity, cellular redox, and binding; biological processes terms involving the cell or subcellular processes; and cellular component terms concerned with membrane function and photosynthesis. These findings are in agreement with other studies [ 30 , 31 , 32 , 33 , 34 , 35 ] and suggest that the genes associated with these GO terms might be involved in drought tolerance. Notably, DEGs relating to photosynthesis, including genes involved in the photosystem, photosynthetic membrane, photosystem II, photosynthesis, photosystem I reaction center, photosystem II oxygen evolving complex, and photosystem I, were typically down-regulated under drought stress, indicating that photosynthetic functions were inhibited (especially from 5 d on).…”

Transcriptome sequencing and metabolome analysis reveal the molecular mechanism of Salvia miltiorrhiza in response to drought stress

“…Plant-pathogen interactions, which exhibit two patterns, PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI), are crucial physiological processes that occur in plants [ 43 ]. It has been reported that drought stress could trigger the plant-pathogen interaction and regulate the expression of genes implicated in this pathway, such as FLS2, CNGCs and SGT1 [ 44 ]. FLS2 (flagellin sensitive 2), which exists in the plasma membrane, is one of the immune signal receptors participating in the plant-pathogen interaction pathway and can cause a decline in ROS [ 45 , 46 ].…”

Integration of mRNA and microRNA analysis reveals the molecular mechanisms underlying drought stress tolerance in maize (Zea mays L.)

“…Furthermore, Song et al. (2021) found that japonica and indica rice exhibit strongly DEGs related to the glutathione metabolic pathway under water shortage conditions, while Qian et al. (2021) found that the expression of DEGs related to starch and sucrose metabolic pathways was increased under drought conditions, indicating their importance in stress tolerance.…”

“…Kumar et al (2020) found that DEGs related to plant hormone signal transduction are regulated under drought stress in mung beans, while Yu et al (2020) found that DEGs related to phenylpropanoid biosynthesis have important regulatory roles under drought stress in foxtail millet. Furthermore, Song et al (2021) found that japonica and indica rice exhibit strongly DEGs related to the glutathione metabolic pathway under water shortage conditions, while Qian et al (2021) found that the expression of DEGs related to starch and sucrose metabolic pathways was increased under drought conditions, indicating their importance in stress tolerance. These findings, together with those of this study, confirm that "plant hormone signal transduction", "phenylpropane biosynthesis", "glutathione metabolism", and "starch and sucrose metabolism" are important pathways in maize responses to drought stress, which further supports the findings of the current study.…”