Proton-pumping pyrophosphatase homeolog expression is a dynamic trait in bread wheat ().

Proton-pumping pyrophosphatases (H-PPases) have been shown to enhance biomass and yield. However, to date, there has been little work towards identify genes encoding H-PPases in bread wheat () (s) and limited knowledge on how the expression of these genes varies across different growth stages and tissue types. In this study, the IWGSC database was used to identify two novel genes, and , and elucidate the complete homeolog sequences of the three known genes, bringing the total number of bread wheat s from 9 to 15. Gene expression levels of each homeolog were assessed using quantitative real-time PCR (qRT-PCR) in four diverse wheat varieties in terms of phenotypic traits related to high vacuolar pyrophosphatase expression. Homeolog expression was analyzed across multiple tissue types and developmental stages. Expression levels of the homeologs were found to vary significantly between varieties, tissues and plant developmental stages. During early development (Z10 and Z13), expressions of and homeologs were higher in shoot tissue than root tissue, with both shoot and root expression increasing in later developmental stages (Z22). was expressed in all varieties and tissue types and was the most highly expressed homeolog at all developmental stages. Expression of the homeologs was restricted to developing grain (Z75), while homeolog expression was higher at Z22 than earlier developmental stages. Variation in was detected among varieties at Z22 and Z75, with Buck Atlantico (high biomass) and Scout (elite Australian cultivar) having the highest levels of expression. These findings offer a comprehensive overview of the bread wheat H-PPase family and identify variation in homeolog expression that will be of use to improve the growth, yield, and abiotic stress tolerance of bread wheat.