Small heat shock proteins genes are differentially expressed in distinct varieties of common bean

Abstract

Plants respond to temperature stress by synthesizing a set of heat shock proteins (HSPs), which may be responsible for the acquisition of thermotolerance. In this study, the induction of small HSPs (sHSPs) in eight common bean varieties was evaluated by Northern blot analysis using the W HSP 16.9 cDNA as heterologous probe. Cowpea was used, as a positive control since this plant, as opposed to common bean, is known to grow well under high temperature regimes such as that found in the Brazilian semi-arid region. After the growth period, the plants were submitted to two h of heat shock at 40°C. All varieties tested were able to induce sHSP mRNAs that hybridized with W HSP 16.9 probe. However, significant kinetic differences were found when comparing different varieties. SHSP mRNA levels induced after heat shock in cowpea was higher than the levels observed on the bean varieties displaying the highest expression of these proteins. Besides, the sHSP expression was also assessed at the protein accumulation level by Western-blot analysis for cowpea and both IPA 7 and Negro Argel varieties of bean plants. The revealed protein pattern confirmed that sHSPs are differentially expressed in distinct varieties of common bean according their heat stress tolerance.