Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 14, 2007
Publication Date: March 1, 2008
Citation: Altenbach, S.B., Kothari, K.M., Tanaka, C.K., Hurkman, W.J. 2008. Expression of 9 kDa lipid transfer protein genes in developing wheat grains is enhanced by high temperature but not by post-anthesis fertilizer. Journal of Cereal Science. 47 (2):201-213. Interpretive Summary: Non-specific lipid transfer proteins (nsLTPs) accumulated in the wheat grain are of interest because they are potential food allergens and also may influence the functional properties of flour. DNA sequences for sixteen different nsLTPs expressed in developing grains of a US wheat variety were identified in public databases. Quantitative methods were developed to measure the accumulation of mRNA corresponding to two of the most prevalent nsLTP sequences. These methods were used to evaluate gene expression in wheat grains produced in greenhouses under a variety of different temperature and fertilizer regimens. Both nsLTP genes were expressed late in grain development and levels of mRNA were significantly higher in grains subjected to high temperatures. The corresponding proteins also accumulated late in grain development and levels were higher in grains produced under high temperatures and in flour obtained from those grains. In contrast, the expression of nsLTP genes was not influenced by the application of fertilizer.
Technical Abstract: A survey of EST databases identified sixteen 9 kDa non-specific lipid transfer proteins (nsLTPs) expressed in developing grains from the US spring wheat Butte 86. Two of the most prevalent sequences encoded nsLTPs similar to proteins identified by two-dimensional gel electrophoresis/mass spectrometry (2-DE/MS) in endosperm tissue and flour. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was used to examine the expression of these nsLTPs in developing grains or endosperm produced under controlled temperature and fertilizer regimens. Under a moderate (24/17oC day/night) temperature regimen, transcripts were accumulated late in grain development and transcripts achieved highest levels as grains reached maximum dry weights. When high temperature regimens (37/28oC day/night) were imposed from anthesis or 15 days post-anthesis (DPA) until maturity, maximum transcript levels were as much as 9-fold higher. Post-anthesis fertilizer had relatively small effects on transcript levels. Accumulation profiles for 9 kDa nsLTPs generated by 2-DE were consistent with transcript profiles. The nsLTPs increased 2 to 3.5-fold in amount in endosperm in response to high temperatures but showed little change in response to fertilizer. Increases in the amounts of 9 kDa nsLTPs also were observed in flour from grains produced under the high temperature regimens.