Structure and Light-Induced Expression of a Small Heat-Shock Protein Gene of Pharbitis nil

Abstract

To isolate genes that are regulated by a photoperiod that promotes flowering in Pharbitis nil, a cDNA library representing mRNA of induced cotyledons was screened by differential hybridization. The DNA sequence of one cDNA clone isolated by this approach, clone 12L, showed homology to plant small heat-shock protein (hsp) genes. P. nil genomic clones hybridizing to clone 12L were isolated, and the DNA sequences of two P. nil small hsp (shsp) genes, shsp-1 and shsp-2, were determined. The derived amino acid sequences of shsp-1 and shsp-2 showed maximum homology to the 17.9-kD soybean hsp, a member of the class 11 cytoplasmic hsps found in plants. A The physiological processes in floral initiation can be divided into three steps: photoperiodic perception by cotyledons, translocation of induced floral stimulus to the shoot tip where floral initiation takes place, and evocation that results in the commitment of the meristem to form flowers. RNA synthesis in cotyledons, in response to the inductive photoperiod, has been suggested as a necessary part of floral induction in P. nil (1, 31). Recently, more direct molecular approaches have been applied to the study of changes in gene expression associated with the photoperiodic induction of flowering. Both qualitative and quantitative differences were found between translatable mRNAs isolated from cotyledons of plants kept in continuous light and from cotyledons of plants that received an inductive dark period (16).To isolate genes whose expression in P. nil cotyledons is regulated by a photoperiod that leads to flowering, we used a differential screening procedure. We report the isolation, sequence, and expression of one of the genes isolated by this approach. We demonstrate that this gene is a member of a multigene family and can potentially encode a low molecular mass hsp4. Expression of one member of this family is regulated by heat shock and by light, and expression of a related member is regulated only by heat shock. MATERIALS AND METHODS PlantsPharbitis nil plants were grown at 230C for 5 d in coolwhite fluorescent light (145 gE m-2 s-1). At this time, they were subjected to an inductive dark period of 12 or 14 h and were subsequently kept in light for 2 h. The cotyledons were excised, and RNA was extracted as described below. Plants that received a red light night break were exposed to 20 min of red light at the 7th hour of the dark treatment.

The expanding small heat-shock protein family, and structure predictions of the conserved “α-crystallin domain”

“…Both are encoded by one open reading frame. In the noncoding region of both genes several heat-shock elements were found (Krishna et al 1992). The Chenopodium rubrum 18.3-kDa shsp belongs to the cytosolic shsp subfamily (class I).…”

“…For example, in Pharbitis nil, one of the shsp genes is induced by heat shock only, the other by light as well (Krishna et al 1992). The expression of smaller hsp27 transcripts in murine osteoblasts, which may be encoded by separate genes, was facilitated by estrogen treatment prior to heat shock, whereas expression of the normal, longer, hsp27 was induced by heat shock alone (Cooper and Uoshima 1994).…”

Effects of pure microcystin-LR on the transcription of immune related genes and heat shock proteins in larval stage of zebrafish (Danio rerio)

“…When organisms are exposed to a variety of stress factors such as cold, heat, CO 2 , heavy metal, and various chemicals (Hoffmann and Parsons, 1991;Krishna et al, 1992;Ferrando et al, 1995), they synthesize a set of heat shock proteins (HSPs), which usually act as molecular chaperones, and play diverse roles in transporting, folding, assembling of degraded or misfolded proteins (Johnston et al, 1998;Sφrensen et al, 2003). Heat shock proteins, particularly HSP70, have been proposed as biochemical markers of environmental stress, such as toxicant exposure, in aquatic species .…”

Interaction between Short-Term Heat Pretreatment and Fipronil on 2ndInstar Larvae of Diamondback Moth,Plutella Xylostella(Linn)

“…In the environment, organisms are often exposed to various stresses such as heat, cold, desiccation, CO 2 , heavy metals, and different chemical poisons (Lindquist 1986;Hoffmann and Parsons 1991;Krishna et al 1992;Ferrando et al 1995). Among all these stresses, temperature is the most important factor that affects the abundance and distribution of organisms as well as their populations (Cossins and Bowler 1987;Clarke 2003;Hoffmann et al 2003).…”