Genes encoding the PR-4 protein wheatwin are developmentally regulated in wheat grains and respond to high temperatures during grainfill

Sequences encoding three wheatwins, including a novel protein not identified previously, were found among expressed sequence tags (ESTs) from grain from the US bread wheat Butte 86 and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was used to detect transcripts specific for two of the wheatwins in a variety of tissues. In the absence of pathogen challenge, wheatwin transcripts were detected in embryo, endosperm, whole grain, awns and glumes as well as in leaves, stems and roots. In both whole grain and endosperm, transcripts accumulated late in development and achieved the highest levels as grain reached maximum dry weight. When high temperature regimens (37/28 °C day/night) were imposed during grain development, the timing of transcript accumulation was compressed and maximum transcript levels were significantly higher than under a moderate 24/17 °C day/night regimen. Accumulation profiles for two wheatwin proteins identified in endosperm by 2-DE/MS were consistent with transcript profiles and flour from grain produced under high temperatures had greater amounts of the two proteins than flour from grain produced under moderate temperatures. The data confirm that wheatwin genes are developmentally regulated in the grain and suggest that wheatwin plays a role in the response of the developing grain to high temperatures in addition to its protective role against fungal pathogens. Enhanced expression of wheatwin genes in grain produced under high temperature conditions may have important implications for wheat flour quality and allergenic potential.