Identification and characterization of 20S proteasome genes and their relevance to heat/drought tolerance in bread wheat

The genes encoding alpha-and beta-type subunits of 20S proteasome core protease are integral components of 26S proteasome complex in the ubiquitin-proteasome system (UPS). The 20S proteasome represents a catalytic particle that cleaves cytotoxic, denatured, damaged and unwanted proteins in an ATP/ubiquitin-dependent nonlysosomal pathway and is known to impart thermotolerance in model plants. In the present study, we identified 67 genes (including 34 TaPA + 33 TaPB genes) encoding alpha- and beta-subunits of 20S proteasome in bread wheat (Triticum aestivum L.). These genes were distributed on all the 21 wheat chromosomes, majority of them being in triplicate homoeologues. These wheat genes were orthologous to corresponding rice and Arabidopsis genes. Phylogenetic analysis placed these genes in seven clusters, each with one of the seven alpha (alpha 1-7) and one of the seven beta (beta 1-7) subunits. Expression analysis suggested that 10 of the 67 genes were involved in heat stress response, whereas four genes were involved in drought tolerance at the seedling stage. Nine (9) genes were expressed under both heat and drought suggesting their involvement in response to multiple abiotic stresses. Hopefully, future research on TaPA/TaPB genes, will help in the development of climate resilient wheat cultivars.

Automated summary

This study identified 67 genes encoding alpha- and beta-subunits of 20S proteasome in bread wheat and found that they are distributed on different chromosomes. Some of these genes are involved in heat stress and drought tolerance, which can contribute to the development of climate resilient wheat cultivars.