Abstract
BackgroundWheat grains accumulate a variety of low molecular weight proteins that are inhibitors of alpha-amylases and proteases and play an important protective role in the grain. These proteins have more balanced amino acid compositions than the major wheat gluten proteins and contribute important reserves for both seedling growth and human nutrition. The alpha-amylase/protease inhibitors also are of interest because they cause IgE-mediated occupational and food allergies and thereby impact human health.ResultsThe complement of genes encoding alpha-amylase/protease inhibitors expressed in the US bread wheat Butte 86 was characterized by analysis of expressed sequence tags (ESTs). Coding sequences for 19 distinct proteins were identified. These included two monomeric (WMAI), four dimeric (WDAI), and six tetrameric (WTAI) inhibitors of exogenous alpha-amylases, two inhibitors of endogenous alpha-amylases (WASI), four putative trypsin inhibitors (CMx and WTI), and one putative chymotrypsin inhibitor (WCI). A number of the encoded proteins were identical or very similar to proteins in the NCBI database. Sequences not reported previously included variants of WTAI-CM3, three CMx inhibitors and WTI. Within the WDAI group, two different genes encoded the same mature protein. Based on numbers of ESTs, transcripts for WTAI-CM3 Bu-1, WMAI Bu-1 and WTAI-CM16 Bu-1 were most abundant in Butte 86 developing grain. Coding sequences for 16 of the inhibitors were unequivocally associated with specific proteins identified by tandem mass spectrometry (MS/MS) in a previous proteomic analysis of milled white flour from Butte 86. Proteins corresponding to WDAI Bu-1/Bu-2, WMAI Bu-1 and the WTAI subunits CM2 Bu-1, CM3 Bu-1 and CM16 Bu-1 were accumulated to the highest levels in flour.ConclusionsInformation on the spectrum of alpha-amylase/protease inhibitor genes and proteins expressed in a single wheat cultivar is central to understanding the importance of these proteins in both plant defense mechanisms and human allergies and facilitates both breeding and biotechnology approaches for manipulating the composition of these proteins in plants.
Highlights
Wheat grains accumulate a variety of low molecular weight proteins that are inhibitors of alphaamylases and proteases and play an important protective role in the grain
To link individual protein spots from the Dupont et al [17] study to the precise DNA sequences for alpha-amylase/protease inhibitors from Butte 86, we have examined the complement of genes expressed in Butte 86 by assembling expressed sequence tag (EST) from this cultivar
Ninety-seven ESTs from the US hard red spring wheat Butte 86 were assembled into 19 contigs encoding low molecular weight alpha-amylase/protease inhibitors (Table 1, Additional files 1, 2)
Summary
Wheat grains accumulate a variety of low molecular weight proteins that are inhibitors of alphaamylases and proteases and play an important protective role in the grain. Wheat kernels accumulate a variety of low molecular weight proteins that inhibit amylases and/or proteases from different sources. A number of other proteins share structural similarities to the alpha-amylase inhibitors but are active against specific proteases Far, these proteins have been characterized in barley and other cereals, but not in wheat. All of the mature alphaamylase/protease inhibitor proteins contain 10 cysteine residues that form five disulfide bonds Proteins in another class, referred to as WASI, inhibit endogenous alpha-amylases. Vinjett subjected to different combinations of temperature and water stress
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