Gene Expression Analysis of Heat-Shock Proteins in Boechera lemmonii, Boechera sparsiflora, Boechera pulchra, and Boechera perennans When Exposed to Various Degrees of Heat Stress

Plants frequently are subject to heat stress, and this stress is known to negatively impact plant growth and agronomic yield. High temperature stress induces the heat shock proteins (HSPs).  HSPs are molecular chaperones that aid other proteins so that they can function normally in stressful conditions. They assist other proteins with folding and prevent irreversible aggregation. This molecular machinery is vital for an organism to maintain homeostasis. It has been demonstrated that HSPs are expressed at higher levels in plants as they are exposed to higher levels of heat stress. We have examined the thermotolerance of ten-day old Arabidopsis thaliana and Boechera seedlings to both basal and acquired heat stress at temperatures ranging from 22°C to 45°C.  Variation was found in the thermotolerance of these species to heat stress. All the Boechera species were more thermotolerant than Arabidopsis. In addition, the four Boechera species varied among themselves in their ability to tolerate heat stress. In order to more fully understand the role of the HSPs in thermotolerance we examined, with both PCR and QPCR, the gene expression patterns of key HSPs.  We have determined the  temperature needed for induction of HSP21 for B. lemmonii, B. sparsiflora, B. pulchra, and B. perennans. QPCR data has been obtained for HSP21 and HSP101 in Arabidopsis and gene expression levels peak at about 38°C and then decrease at 40°C in Arabidopsis. We are currently examining these key HSPs and their expression during heat stress in the Boechera species.