Transcriptomic and Physiological Responses of Qingye Ramie to Drought Stress

Qingye ramie is a multi-purpose crop, used as a feed ingredient in southern China, that is susceptible to drought. Qingye ramie was studied to investigate the effects of high temperatures and drought on its growthh. The results show that, after drought, ramie leaves turn yellow and that the height of the plant, the number of tillers, and its antioxidant activity decreased. To elucidate the molecular mechanism of drought tolerance, we performed RNA sequencing (RNA-seq) on drought-stressed samples and found that 3893 differentially expressed genes showed significant changes; 1497 genes were upregulated, and 2796 genes were downregulated. These genes were categorized into four metabolic pathways and were mainly enriched in plant hormone signal transcription, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, and starch and sucrose metabolism. Among these, we mapped the regulatory mechanism of Qingye ramie under drought and adversity. Of these, the expression of MAPK-related genes in the plant hormone pathway was the most significant. The expression of three MAPK serine/threonine protein kinase genes was upregulated by 2.62- to 3.45-fold and the expression of PP2C-related genes increased by 3.34- to 14.12-fold. The expression of PYR/PYL genes decreased significantly by 2.92-7.09-fold. Furthermore, in addition to NAC, ERF, MYB, bHLH, bZIP, C2H2, GeBP, and WRKY transcription factors that have been shown to regulate drought. Some other transcription factors, such as CCL, ASD, SAU, and SPS, were also up- or downregulated in Qingye ramie. Then, the samples were analyzed by qRT-PCR and the variations were consistent with the sequencing results. Consequently, we suggest that the changes after drought stress in green-leaf ramie may be regulated by these transcription factors. Further studies can be carried out in the future, which will provide valuable and important information on the plant's drought resistance mechanism and deepen our understanding of the mechanisms of drought resistance in Qingye ramie.