Comparative analysis of heat-stress-induced abscisic acid and heat shock protein responses among pea varieties

Heat shock proteins (HSPs) and abscisic acid (ABA) play important roles in plant heat responses but have not been extensively studied in pea (Pisum sativum L.), whose heat susceptibility is well known. In this study, four pea varieties varying in heat tolerance based on field trials were evaluated. Plants were heat stressed for 3, 6, 12, or 24 h at 38 degrees C before pollination. Anther and stipule RNA from the same flowering node were sampled for transcriptional profiling of PsHSP18.1 and PsHSP71.2. Additional stipules were sampled for the quantification of ABA concentration and its five key catabolites from the four major ABA catabolic pathways by ultra-high performance liquid chromatography-selected reaction monitoring mass spectrometry (UHPLC-SRM/MS). The transcription of both HSP genes was upregulated because of heat stress (HS). In stipules, the upregulation was greatest at 3 h HS, whereas in anthers, the induced transcription was similar among different hours of HS. Likewise, more ABA accumulated in the ABA metabolism pool because of HS, and the ABA response started rapidly after 3 h of treatment. Heat-tolerant varieties had a higher ABA synthesis and turnover rate at 3 h HS than their respective heat-susceptible counterparts. This study provides new insights into different heat tolerance among Canadian pea varieties regarding HSP and ABA hormone regulation.