It is known that HSP70 plays an important role in the antiischaemic effect of adaptation to stress. The aim of our study was to verify the hypothesis that nitric oxide (NO) may contribute to the activation of HSP70 synthesis and to enhance thereby the resistance of organism to the ischaemic and reperfusion damages. We observed that heat shock potentiated NO production in the heart NO formation was completely blocked by the NO synthase inhibitor N^-nitro-L-arginine (L-NNA). L-NNA also significantly attenuated the heat shock-induced accumulation of HSP70 (by 45 % in heart). Both heat shock and NO donor induced time- and concentration-dependent HSP70 synthesis in the culture of human hepatoblastoma cells Hep G2. Prior injection of NO donor (30-100 mg per rat) exerted a dose- dependent protective effect on the isolated heart in ischaemia and reperfusion within 24 hours. We suggest that NO is involved in the activation of HSP70 synthesis which can play an important role in the delayed protective effect of NO donors.
We recently showed that the chloroplast small heat-shock protein (herein referred to as chlp Hsp24) protects photosystem 2 (PS2) during heat stress, and phenotypic variation in production of chlp Hsp24 is positively related to PS2 thermotolerance. However, the importance of chlp Hsp24 or other Hsps to other aspects of photosynthesis and overall photosynthetic thermotolerance is unknown. To begin investigating this and the importance of genetic variation in Hsp production to photosynthetic thermotolerance, the production of several prominent Hsps and photosynthetic thermotolerance were quantified in nine genotypes of Lycopersicon, and then the relationships between thermotolerance of net photosynthetic rate (PN) and production of each Hsp were examined. The nine genotypes exhibited wide variation in PN thermotolerance and production of each of the Hsps examined (chlp Hsp70, Hsp60, and Hsp24, and cytosol Hsp70). No statistically significant relationship was observed between production of chlp Hsp70 and PN thermotolerance, and only a weak positive relationship between cytosolic Hsp70 and P N was detected. However, significant positive relationships were observed between production of chlp Hsp24 and Hsp60 and PN thermotolerance. Hence natural variation in production of chlp Hsp24 and Hsp60 is important in determining variation in photosynthetic thermotolerance. This is perhaps the first evidence that chlp Hsp60 is involved in photosynthetic thermotolerance, and these in vivo results are consistent with previous in vitro results showing that chlp Hsp24 protects PS2 during heat stress. and P. J. Preczewski ... [et al.].
Rice being the major food crop for more than half of the world population is severely affected by drought stress starting from the establishment of the seedling. We focused on the UV-B priming mediated transgenerational drought tolerance of a drought-tolerant rice variety (Vaisakh) towards polyethylene glycol (PEG) 6,000 (20%)-induced drought. Results showed that priming in F0 generation and re-priming in F1 generation with UV-B enhanced the PEG stress tolerance potential of rice seedlings with increased expression of genes encoding antioxidant enzymes and stress-related proteins offering better protection to primed plants. UV-B priming maintained oxidative homeostasis of the plant cell thus ensuring uninterrupted mitochondrial and photosynthetic activities. Cumulatively, our results suggest that the transgenerational priming memory retained in the seeds is transferred to offspring without any loss. Moreover, re-priming in F1 generation further boosted the innate tolerance potential of a tolerant variety resulting in stable cellular redox homeostasis.