Small Heat Shock Proteins Can Release Light Dependence of Tobacco Seed during Germination

Abstract

Small heat shock proteins (sHSPs) function as ATP-independent molecular chaperones, and although the production and function of sHSPs have often been described under heat stress, the expression and function of sHSPs in fundamental developmental processes, such as pollen and seed development, have also been confirmed. Seed germination involves the breaking of dormancy and the resumption of embryo growth that accompany global changes in transcription, translation, and metabolism. In many plants, germination is triggered simply by imbibition of water; however, different seeds require different conditions in addition to water. For small-seeded plants, like Arabidopsis (Arabidopsis thaliana), lettuce (Lactuca sativa), tomato (Solanum lycopersicum), and tobacco (Nicotiana tabacum), light is an important regulator of seed germination. The facts that sHSPs accumulate during seed development, sHSPs interact with various client proteins, and seed germination accompanies synthesis and/or activation of diverse proteins led us to investigate the role of sHSPs in seed germination, especially in the context of light dependence. In this study, we have built transgenic tobacco plants that ectopically express sHSP, and the effect was germination of the seeds in the dark. Administering heat shock to the seeds also resulted in the alleviation of light dependence during seed germination. Subcellular localization of ectopically expressed sHSP was mainly observed in the cytoplasm, whereas heat shock-induced sHSPs were transported to the nucleus. We hypothesize that ectopically expressed sHSPs in the cytoplasm led the status of cytoplasmic proteins involved in seed germination to function during germination without additional stimulus and that heat shock can be another signal that induces seed germination.

Improving seed germination of the eggplant rootstock Solanum torvum by testing multiple factors using an orthogonal array design

“…Similarly, applications of the plant growth regulator GA 3 or KNO 3 are efficient at releasing Solanum seeds from dormancy and stimulating germination (Hayati et al, 2005;Wei et al, 2010;Gisbert et al, 2011a). Light irradiation, which is an important regulator of seed germination in solanaceous species (Koo et al, 2015), has also been observed to be efficient at stimulating germination in S. torvum seeds. Amazingly, the scarification by NaClO had a highly negative effect on germination.…”

Comparative analysis of nine different small heat shock protein gene promoters in Oryza sativa L. subsp. indica

“…The mRNAs from heat shock genes have structures that allow for their selective translation in a stressed cell Mahmood et al 2010). These include a lack of introns, 5 0 -untranslated regions conferring translational efficiency, and 3 0 -untranslated regions providing increased stability (Koo et al 2015). Keeping in view the importance of small heat shock proteins (sHSPs), the present study was designed to identify and compare nine different sHSP gene promoters from rice.…”

Varied expression pattern of the small heat shock protein gene encoding HSP17.7 against UVA, UVB, Cu²⁺and Zn²⁺stresses in sunflower

“…Heat shock proteins (HSPs), also known as molecular chaperones, are known to belong among these stress proteins while they are present in all living organisms (Kim & Hwang 2015). Besides their role in protecting cells against environmental stress conditions, HSPs are essential components of plant cells and they play an important role in protein stabilisation and cellular functions related with plant growth (Pratt et al 2001;Koo et al 2015).…”

“…In plants, they are classified into five evolutionarily conserved families: HSP100,90,70,60 (or chaperonins), and the small HSPs (sHsps) which have molecular weights of 100, 90, 70, 60, and 12-40 kDa, respectively (AlWhaibi 2011;Koo et al 2015). Higher plants are known to have at least 20 types of sHsps which have an α-crystallin domain consisting of 80-100 amino acid residues in the C-terminal region (Seo et al 2006).…”