Bletilla striata is a valuable Chinese herbal medicinal plant widely used in various fields. To meet the market demand for this herb, the tissue culture technology of B. striata was developed. However, drought stress has been a significant threat to the survival of cultivated B. striata. To further understand the underlying mechanisms of B. striata under drought stress, its response was investigated at the physiological and transcriptional levels. Our photosynthesis results show that the decline of the net photosynthesis rate (Pn) in B. striata leaves was mainly caused by nonstomatal limitation factors. Using transcriptomic analysis 2398, differentially expressed genes (DEGs) were identified. KEGG enrichment analysis showed that DEGs involved in plant hormone signal transduction (ko04075) were significantly altered, especially the abscisic-acid signaling pathway. The up-regulations of the serine/threonine protein kinase (SnRK2) and S-type anion (SLAH2) channels might lead to stomatal closure, which is the reason for decline of photosynthesis. Moreover, the downregulation of cytochrome b6 and photosystem I reaction center subunit III/IV might be the major reason for nonstomatal limitation. In addition, B. striata enhanced the ability of ROS scavenging via activating the gene expression of superoxide dismutase, catalase, and peroxidase in response to drought stress. Our study enhanced the understanding of B. striata in response to drought stress.

Background: Peperomia leptostachya is a herbaceous plant with significant medicinal value. To elucidate its mitochondrial genomic characteristics, this study conducted a systematic analysis. Methods: The mitochondrial genome of P. leptostachya was assembled, annotated, and subjected to comparative analysis. Results: (1) The genome exhibits significant structural peculiarities, presenting as an atypical circular structure accompanied by an independent minicircle, forming a multi-branched reticulate configuration spanning a total length of 981,249 bp. Within the mitochondrial genome of P. leptostachya, a total of 52 genes have been identified, including 35 PCGs, 14 tRNAs and 3 rRNAs. (2) A phylogenetic tree was built for 22 species based on the DNA sequences. P. leptostachya belongs to the family Piperaceae within the order Piperales and is closely related to Piper nigrum. (3) Homologous colinear blocks were detected between P. leptostachya and its close relatives, though these blocks exhibited short lengths. Additionally, blank regions were identified that showed no homology with other species. Mitochondrial genomes of P. leptostachya and two close relatives had inconsistent collinear block arrangements. The mitochondrial genome of P. leptostachya had undergone genomic rearrangement relative to closely related species. Conclusions: This study lays the foundation for research into the genetic characteristics and biological traits of P. leptostachya.