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To understand stress response mechanisms, a multiple stress-responsive gene OsPM1 with a disordered region containing about 30 amino acid residues was screened by microarray. Promoter region analysis using PlantCARE showed this gene contains multiple cis-regulatory elements responding to abiotic stresses. Quantitative real-time PCR and promoter-GUS transgenic plant analysis verified that OsPM1 was induced by multiple abiotic stresses. OsPM1-GFP fusion protein expression showed that OsPM1 was localized at the cell membrane. The rice plants overexpressing OsPM1 exhibited hypersensitivity to salt stress but enhanced drought tolerance compared to the wild-type plants; the rice plants expressing antisense of OsPM1 were hyposensitive to salt stress but with weak drought tolerance compared to the wild-type plants. These results showed OsPM1 is a positive regulator of rice tolerance to drought, but it’s also a negative regulator of rice tolerance to salt.

Drought stress affects the normal growth and development of Mesona chinensis Benth (MCB), which is an important medicinal and edible plant in China. To investigate the physiological and molecular mechanisms of drought resistance in MCB, different concentrations of polyethylene glycol 6000 (PEG6000) (0, 5, 10, and 15%) were used to simulate drought conditions in this study. Results showed that the growth of MCB was significantly limited under drought stress conditions. Drought stress induced the increases in the contents of Chla, Chlb, Chla + b, soluble protein, soluble sugar, and soluble pectin and the activities of superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (TAC), hydrogen peroxide (H2O2), and malondialdehyde (MDA). Transcriptome analysis revealed 3,494 differentially expressed genes (DEGs) (1,961 up-regulated and 1,533 down-regulated) between the control and 15% PEG6000 treatments. These DEGs were identified to be involved in the 10 metabolic pathways, including “plant hormone signal transduction,” “brassinosteroid biosynthesis,” “plant–pathogen interaction,” “MAPK signaling pathway-plant,” “starch and sucrose metabolism,” “pentose and glucuronate interconversions,” “phenylpropanoid biosynthesis,” “galactose metabolism,” “monoterpenoid biosynthesis,” and “ribosome.” In addition, transcription factors (TFs) analysis showed 8 out of 204 TFs, TRINITY_DN3232_c0_g1 [ABA-responsive element (ABRE)-binding transcription factor1, AREB1], TRINITY_DN4161_c0_g1 (auxin response factor, ARF), TRINITY_DN3183_c0_g2 (abscisic acid-insensitive 5-like protein, ABI5), TRINITY_DN28414_c0_g2 (ethylene-responsive transcription factor ERF1b, ERF1b), TRINITY_DN9557_c0_g1 (phytochrome-interacting factor, PIF3), TRINITY_DN11435_c1_g1, TRINITY_DN2608_c0_g1, and TRINITY_DN6742_c0_g1, were closely related to the “plant hormone signal transduction” pathway. Taken together, it was inferred that these pathways and TFs might play important roles in response to drought stress in MCB. The current study provided important information for MCB drought resistance breeding in the future.

To study the effects of light quality and salt stress on RNA editing of Mesona chinensis Benth (MCB) chloroplast genome, the RNA editing sites in the MCB chloroplast protein-coding genes were predicted and then partially verified by PCR and RT-PCR. Meanwhile, the RNA editing efficiency and relative expression of accD, ndhB, ndhF, and rpoB under red and blue light and salt stress conditions were analyzed. A total of 45 editing sites were predicted and all the editing sites were C-to-U conversion. 12 predicted editing sites were verified. The expression level of accD was down-regulated under red light compared with the blue light, as well as down-regulated under salt stress compared with the normal condition (CK). Additionally, the editing efficiency of accD-287 was 96.7% under normal condition, higher than that under salt stress (93.3%) but lower than those under blue and red light (both 100%). In ndhB, ndhB-494 was partially edited under normal growth condition but completely edited under blue and red light and salt stress, and other sites were completely edited under all conditions. It was indicated that the editing frequency was not positively relevant to the transcript level. Besides, accD-287 and ndhB-494 might be involved in response to salt stress.