Patterns of thermotolerance, chlorophyll fluorescence, and heat shock gene expression vary among fourBoecheraspecies andArabidopsis thaliana

Abstract

Thermotolerance is a property of all organisms, but owing to their sessile nature, this trait is particularly important in plants. Basal thermotolerance is based on inherent tolerance to heat stress. Acquired thermotolerance is attained through stress-induced gene expression, often of those genes encoding heat shock proteins (HSPs). Both basal and acquired thermotolerance have been extensively studied in model species such as Arabidopsis thaliana (L.) Heynh., but much less is known about thermotolerance in wild plant species. The aims of this study were to examine the basal and acquired thermotolerance of four species of Boechera, and of A. thaliana. Four species of Boechera native to California were collected and used for this study: B. arcuata (Nutt.) Windham & Al-Shehbaz, B. californica (Rollins) Windham & Al-Shehbaz, B. depauperata (A.Nelson & P.B.Kenn.) Windham & Al-Shehbaz, and B. perennans (S.Watson) W.A.Weber. Seedlings were exposed to both basal and acquired heat stress and then monitored for leaf damage, chlorophyll fluorescence, and gene expression of HsfA3, Hsp101, and four sHSP genes. Analysis of organismal responses to heat stress demonstrated that all four Boechera species are more thermotolerant than A. thaliana. Further we found that he species with the highest thermotolerance is B. depauperata.