Abstract
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.
Highlights
Drought is a complex and natural phenomenon mainly caused by less precipitation in a certain period, which has the characteristics of frequency, intensity, and duration (Mishra and Singh, 2010)
The contents of Chlorophyll a (Chla), chlorophyll b (Chlb), Chla + b, soluble protein, soluble sugar, and soluble pectin were significantly increased with the increasing concentration of PEG6000 (Figure 3), which were positively correlated to PEG6000 concentration
The fresh weight of the whole plant, root, and aboveground was significantly decreased, while the contents of Chla, Chlb, Chla + b, soluble protein, soluble sugar, soluble pectin, superoxide dismutase (SOD), CAT, total antioxidant capacity (TAC), MDA, and H2O2 were dramatically increased with the increasing concentrations of PEG6000
Summary
Drought is a complex and natural phenomenon mainly caused by less precipitation in a certain period, which has the characteristics of frequency, intensity, and duration (Mishra and Singh, 2010). Drought stress affects the water relations of plants at the cellular, tissue, and organ levels causing physical damage, physiological and biochemical disruptions, and molecular changes (Beck et al, 2007) like photosynthesis, respiration, antioxidant, hormonal metabolism, and gene expression (Bhargava and Sawant, 2013). Plants can reduce osmotic potential through the accumulation of osmotic substances (Bray, 1993), such as proline, soluble sugar, betaine, organic acid, free amino acid, and other organic substances (Wang et al, 2010) to maintain the normal water demand and promote drought tolerance. Drought stress can disturb the self-regulation balance of cells, lead to the excessive accumulation of reactive oxygen species (ROS), cause membrane peroxidation, changes in membrane fluidity and ion transport, damage of biological macromolecules, destruction of chloroplast structure, metabolic disorder, and result in plant death (Gill and Tuteja, 2010). The plant hormone ABA plays a central role
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