Differential gene expression in Festuca under heat stress conditions

Abstract

Fescues (Festuca sp.) are major cool-season forage and turf grass species around the world. Heat stress is one of the limiting factors in the production of fescues as forage in the southern Great Plains of the US. Heat responsive gene transcripts were cloned by using suppression subtractive hybridization between a heat-tolerant and a heat-sensitive fescue genotype subjected to a slowly increased temperature mimicking the natural conditions. The temperature in the growth chamber containing the plants was gradually increased from 24 degrees C to 44 degrees C over a period of 2 weeks. Three subtractions were conducted between samples of the two genotypes collected after 12 h of exposure to 39, 42, and 44 degrees C. A total of 2495 ESTs were generated, of which 1800 clustered into 434 contigs and 656 were singlets. The putative functions of ESTs were predicted by BLASTX. Nearly 30% of the contigs and 39% of the singlets had no similarity to GenBank sequences. Differentially expressed genes selected by subtractions were classified into 10 broad categories according to their putative functions generated by BLAST analysis. Under heat-stress conditions, cell maintenance, chloroplast associated and photosynthesis-, protein synthesis-, signalling-, and transcription factor-related genes had higher expression levels in the heat-tolerant genotype. Genes related to metabolism and stress had higher expression in the heat-sensitive genotype. The expression of 17 selected gene transcripts were examined by RT-PCR using plant tissues of the two genotypes grown under heat stress and under optimal temperature conditions (24 degrees C) for fescue. Results from RT-PCR confirmed the differential expressions of these transcripts. The differential expressions of at least 11 of these genes were attributable to heat stress rather than to differences in the genetic backgrounds of the genotypes.

Understanding the molecular events underpinning cultivar differences in the physiological performance and heat tolerance of cotton (Gossypium hirsutum)

“…2) for Sicala 45, which is consistent with previous research detecting cultivar specificity for HSP levels in glasshouse-grown cotton using a protein extraction assay (de Ronde et al 1993) and Festuca species using global transcript profiling (Zhang et al 2005). Furthermore, transcript levels for genes encoding HSPs that interact specifically with electron transfer through photosynthetic (CO072814) and respiratory (DT545357) pathways were higher for Sicala 45 compared with Sicot 53 during the initial stages of heat stress (Fig.…”

“…They were also differentially expressed between the two cultivars, with implications for leaf-level physiological performance and genotype-specific heat tolerance. This finding complements previous research showing genotypic differences for the molecular abiotic stress response in various cropping species (Sahi et al 2003;Zhang et al 2005;Dev Sharma et al 2006) and suggests genotypic differences for the relative expression of genes associated with various physiological pathways under heat stress for cotton cultivars. Identification of genotype-specific responses to heat stress for cultivars that have been previously physiologically characterised for heat tolerance provides a framework for further studies using molecular and physiological profiling for identification of and breeding for improved performance in warm and hot environments.…”

“…Although protective proteins involved in photosynthetic and respiratory pathways were upregulated under heat stress (Table 1), the decreased expression of 90 genes associated with the electron flow and ATP pathways (Fig. 1) implied a decreased capacity for photosynthesis and energy availability during heat stress (Rizhsky et al 2002;Zhang et al 2005). These data reflect previously measured decreased electron transport, photosynthesis and Rubisco activase (Cottee et al 2012).…”

“…These trends are consistent with the initial heat stress response of potato (Rensink et al 2005), tobacco (Rizhsky et al 2002), sunflower (Hewezi et al 2008), Festuca sp. (Zhang et al 2005) and A. thaliana (Rizhsky et al 2004;Busch et al 2005;Lim et al 2006;Kant et al 2008), and indicate that plants respond at a molecular level in a similar manner to temperatures well above their thermal optimum.…”

“…2) and greater downregulation of a gene associated with phosphofructo-1-kinase for Sicala 45 (Fig. 2) compared with Sicot 53 may indicate differences in the reliance on alternative energy pathways such as glycolysis and lipid degradation for heatsensitive cotton cultivars under high temperature stress (Zhang et al 2005). Downregulation of genes associated with glycolysis and the oxidative pentose pathway under heat stress in this experiment (Table 1) is in contrast to increased reliance on these pathways for tobacco under heat stress (Rizhsky et al 2002), indicating alternate mechanisms of heat alleviation in various plant species and highlighting the importance of profiling various crop species for performance under heat stress (Boscaiu et al 2012).…”