Abstract
Wheat breeding nowadays must address producers and consumers' desire. According to the last FAO report, a dramatic decrease in wheat production is expected in the next decades mainly due to the upcoming climate change. The identification of the processes which are triggered by heat stress and how thermotolerance develops in wheat is an active research topic. Genomic approach may help wheat breeding since it allows direct study on the genotype and relationship with the phenotype. Here the isolation and characterization of four members of the chloroplast-localized small heat shock proteins (sHSP) encoded by the Hsp26 gene family is reported. Furthermore, two high throughput TILLING (Targeting Induced Local Lesions In Genomes) approaches in vivo and in silico were used for the identification of new alleles within this family. Small heat shock proteins are known to prevent the irreversible aggregation of misfolded proteins and contribute to the acquisition of thermotolerance. Chloroplast-localized sHSPs protect the photosynthetic machinery during episodes of high temperature stress. The modulation of the newly discovered genes within the sHsp26 family has been analyzed in vivo and by the ExpVIP platform widening the abiotic stress analysis; and their involvement in the heat stress response has been demonstrated. In addition, in this study a total of 50 TILLING mutant lines have been identified. A set of KASP (Kompetitive Allele Specific PCR) markers was also developed to follow the specific mutations in the ongoing backcrosses, applicable to high throughput genotyping approaches and usable in marker assisted selection breeding programs.
Highlights
The 50 years are expected to experience both a rise in mean temperatures and a decrease in annual precipitation across the Mediterranean Basin, the extent of which is likely to have a significant impact on agriculture (Field et al, 2012)
A characteristic of all small heat shock proteins (sHSP) is the presence of a central α-crystalline domain (ACD) (Bondino et al, 2012), within which lie two consensus regions (CRI and Conserved Region II (CRII)), determining a β-sheet known to be essential for dimerization and higher order assembly (Poulain et al, 2010)
The matches were grouped on the basis of chromosome position, scaffold and transcript annotation (Table 2) from which the complete putative TaHsp26 gene sequences were reconstructed
Summary
The 50 years are expected to experience both a rise in mean temperatures and a decrease in annual precipitation across the Mediterranean Basin, the extent of which is likely to have a significant impact on agriculture (Field et al, 2012). A number of putative sHSPencoding genes have been isolated in wheat (Weng et al, 1991; Nguyen et al, 1993; Basha et al, 1999; Rampino et al, 2009, 2010, 2012; Pandey et al, 2015) Among these are genes encoding the chloroplast-localized HSP26 proteins, which are ubiquitous throughout the plant kingdom (Ul Haq et al, 2013). HSP26 interacts with photosystem II (Chauhan et al, 2011; Zhang et al, 2014; Hu et al, 2015), thought to be the most thermo-sensitive component of the photosynthetic machinery (Osteryoung and Vierling, 1994; Joshi et al, 1997) Because of their central role more efforts are needed to identify the complete gene sequences encoding for chloroplast sHSPs in Triticum species
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