Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 17, 2007
Publication Date: August 1, 2007
Citation: Altenbach, S.B., Kothari, K.M., Tanaka, C.K., Hurkman, W.J. 2007. Genes encoding the PR-4 protein wheatwin are developmentally regulated in wheat grains and respond to high temperatures during grainfill. Plant Science. 173(2):135-143. Interpretive Summary: Plants synthesize a variety of proteins called pathogenesis-related or PR-proteins that are important in providing protection against invading pathogens. Wheatwin is a PR-protein isolated from wheat flour that has been shown to inhibit the growth of several types of fungi. DNA sequences encoding three different wheatwin proteins expressed in the US bread wheat Butte 86 were identified in public databases. Based on these sequences, quantitative methods were developed to evaluate the expression of two of the genes. Both wheatwin genes were expressed at low levels in a variety of tissues, including leaves, stems, roots, grain and various tissues within the grain and surrounding the grain. In the grain, the expression of wheatwin genes was highest as the grains ripened. When plants were subjected to high temperatures during the period of grain development, the expression of both wheatwin genes was enhanced. The data suggest that wheatwin proteins play important roles in grain development and in the response of the grain to high temperatures in addition to their protective role against pathogens.
Technical Abstract: Sequences encoding three wheatwins, including a novel protein not identified previously, were found among expressed sequence tags (ESTs) from grains 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 grains reached maximum dry weights. When high temperature regimens (37/28oC day/night) were imposed during grain development, the timing of transcript accumulation was compressed and maximum transcript levels were significantly higher. Accumulation profiles for two wheatwin proteins identified in endosperm by 2-DE/MS were consistent with transcript profiles and flour from grains produced under high temperatures had greater amounts of the two wheatwin proteins than flour 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.