The wheat chloroplastic small heat shock protein (sHSP26) is involved in seed maturation and germination and imparts tolerance to heat stress

Abstract

The nuclear-encoded chloroplast small heat shock proteins (sHSPs) are present in all plant species from algae to angiosperms. Expression analysis shows that the wheat chloroplastic sHSP (HSP26) is highly inducible by heat stress in almost all the vegetative and generative tissues and is also expressed constitutively in certain developmental growth stages. We characterize wheat chloroplastic sHSP 26 through transgenic approach using Arabidopsis and report cloning of the promoter and its characterization. Transgenic Arabidopsis plants were substantially tolerant under continuous high temperature regimen than wild-type plants, as measured by photosystem II (PSII) activity, accumulation of more photosynthetic pigments, higher biomass and seed yield. Transgenic plants produced bold seeds under high temperature, having higher germination potential than the wild-type plants. Further, antisense Arabidopsis plants showed negligible tolerance even for non-lethal heat shock, impaired in basal thermo-tolerance, and accumulated less biomass and seed yield under normal growth conditions. Promoter analysis revealed the presence of several heat and other abiotic stress responsive cis-acting elements along with developmental stage and tissue-specific elements. Analysis of promoter through GUS reporter system in both transgenic rice and Arabidopsis further confirms the role of chloroplastic sHsp26 in heat and other abiotic stresses as well as during seed maturation and germination. Genome-wide expression analysis of overexpression Arabidopsis plants revealed that the transcriptome remained unchanged in the transgenic plants and the tolerance was due to the overexpression of chloroplastic heat shock protein (HSP) only.

Improving Photosynthetic Responses during Recovery from Heat Treatments with Brassinosteroid and Calcium Chloride in Indian Bread Wheat Cultivars

“…High temperature treatment resulted in a significant decrease in PSII function in all cultivars after D-1 and D-3 of heat stress. The observable changes in PSII and Fo are dependable diagnostic indicators of photosystem efficiency [44].…”

ABA-INSENSITIVE3, ABA-INSENSITIVE5, and DELLAs Interact to Activate the Expression ofSOMNUSand Other High-Temperature-Inducible Genes in Imbibed Seeds inArabidopsis

“…Other plant hormones, including ethylene, cytokinin, and strigolactone, also promote seed germination at high temperature (Khan and Prusinski, 1989;Matilla, 2000;Kozarewa et al, 2006;Toh et al, 2012). In addition, a number of genetic components (e.g., TRANSPARENT TESTA7, pea [Pisum sativum] G-protein a-and b-subunits, chickpea [Cicer arietinum] APETALA2 [AP2], and wheat [Triticum aestivum] chloroplastic small heat shock proteins) and various chemicals (e.g., CO 2 , 2-4-[carboxyphenyl]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, chlorogenic acid, bovine hemoglobin, isoprene, and glycinebetaine) affect seed germination at high temperature (Saini et al, 1986;Tamura et al, 2006;Misra et al, 2007;Shukla et al, 2009;Hossain et al, 2010;Li et al, 2011;Chauhan et al, 2012). However, the relationships among these components have not yet been clarified.…”

Drying and reduction in sensitivity to desiccation of seeds of Alibertia edulis: the influence of fruit ripening stage

“…2f). The development of germinability during seed ripening is related to different regulatory mechanisms, such as changes in soluble sugar concentration and composition (Verdier et al 2013), decreased nuclear size and chromatin condensation (Zanten et al 2011), and accumulation of heat shock protein (Chauhan et al 2012) and late embryogenesis abundant protein (Dekkers et al 2016). Conversely, seeds originating from green fruits had the lowest germination rate and seedling growth, indicating that seeds were still developing, and that their germination capacity was not fully developed.…”