Abstract
Transglutaminase (TGase) is a regulator of posttranslational modification of protein that provides physiological protection against diverse environmental stresses in plants. Nonetheless, the mechanisms of TGase-mediated salt tolerance remain largely unknown. Here, we found that the transcription of cucumber TGase (CsTGase) was induced in response to light and during leaf development, and the CsTGase protein was expressed in the chloroplast and the cell wall. The overexpression of the CsTGase gene effectively ameliorated salt-induced photoinhibition in tobacco plants, increased the levels of chloroplast polyamines (PAs) and enhanced the abundance of D1 and D2 proteins. TGase also induced the expression of photosynthesis related genes and remodeling of thylakoids under normal conditions. However, salt stress treatment reduced the photosynthesis rate, PSII and PSI related genes expression, D1 and D2 proteins in wild-type (WT) plants, while these effects were alleviated in CsTGase overexpression plants. Taken together, our results indicate that TGase-dependent PA signaling protects the proteins of thylakoids, which plays a critical role in plant response to salt stress. Thus, overexpression of TGase may be an effective strategy for enhancing resistance to salt stress of salt-sensitive crops in agricultural production.
Highlights
Photosynthesis is the basic manufacturing process in plants; it can increase carbon gains and improve crop yield and quality [1]
To investigate the effect of light on the expression of TGase in cucumber plants, we monitored the transcriptional levels of TGase in light-treated cucumber seedlings
To further explore the expression of TGase at different developmental stages, we investigated the transcript levels of TGase in leaves ranging from 1 to 8 weeks old by quantitative real-time PCR
Summary
Photosynthesis is the basic manufacturing process in plants; it can increase carbon gains and improve crop yield and quality [1]. As the polycationic nature of PAs at physiological pH, PAs could be free molecules conjugated with organic acids or bound to negatively charged macromolecules such as proteins, nucleic acids, and chromatin through transglutaminases (TGases) enzymatic activity, stabilizing their structures [8,9]. These interactions are essential for the effects of PAs on plant cell growth and developmental processes and plant response to various stresses. We reveal that TGase has a positive role in PAs accumulation and induce the transcript of photosynthetic genes in chloroplast, which may play crucial roles in the regulation of photosynthetic organ stability. This is the first report to show that the TGase positively regulates plant’s photosynthetic through accumulation of PAs to enhance salt tolerance
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