Expression levels of heat shock proteins through western blot and real-time polymerase chain reaction in maize

High temperature stress (HTS) is one of the most detrimental abiotic stresses which adversely affect productivity of maize (Zea mays L.). Plants respond to HTS by regulating expression of many genes including heat shock proteins (HSPs). We carried out expression analysis of six HSP genes by western blot (WB) and real-time polymerase chain reaction (RT-PCR) in four contrasting Egyptian maize lines, i.e. K1, K7, G342 (heat tolerant) and Rg59 (heat susceptible), subjected to HTS at seedling stage. The six-maize specific HSP genes (ZmHSP70, ZmHSP22, ZmHSP17.9, ZmHSP17.6, ZmHSP16.9 and transcription factor ZIP60) exhibited distinctive expression patterns in response to heat stress (HS). Higher upregulation of ZmHSP70, ZmHSP22, ZmHSP17.9 and ZmHSP17.6 were found throughout the stress exposure at 45°C for 2 and 4 hours in the heat tolerant lines as compared to the control (25°C) and susceptible line. Meanwhile, the susceptible line showed expression of many HSP genes in the control, but these genes were down-regulated by HS. The line K1 showed expression level for ZmHSP70, ZmHSP17.9, ZmHSP17.6 and ZmHSP16.9 genes more than the other lines indicating its highly tolerance against HTS. Higher upregulation of these six genes in the heat tolerant lines indicated their possible role in protecting plant from adverse effects of HS.