Wheat non-specific lipid transfer protein genes display a complex pattern of expression in developing seeds

Abstract

Nine cDNA clones encoding non-specific lipid transfer proteins (nsLTPs) were isolated from Triticum aestivum and Triticum durum cDNA libraries and characterized. One cDNA is predicted to encode a type 2 nsLTP (7 kDa) while others encode type 1 nsLTPs (9 kDa). All encoded proteins contain an N-terminal signal sequence and possess the characteristic features of nsLTPs. The genomic structures of the wheat nsLtp genes show that type 2 TaLtp7.1a, TaLtp7.2a and type 1 TaLtp9.2b genes lack introns while the other type 1 genes consist of one intron. Construction of a phylogenic tree of Poaceae nsLTPs shows that wheat nsLTPs can be divided into eleven distinct groups and are closely related to barley sequences. Using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, the expression patterns of nine nsLtp genes were studied during wheat seed development and germination. We identified three different profiles of nsLtp gene transcript accumulation. Whereas TdLtp7.1a, TdLtp9.4a and TdLtp9.7a transcripts were detected during all maturation stages, TdLtp7.2a, TdLtp9.2a, TdLtp9.3a, TdLtp9.5a and TdLtp9.6a transcripts were only present in the first and TdLtp9.1a in the last stages of seed development. Moreover, these nine wheat nsLtp genes are not seed-specific and are also expressed in the coleoptile of young seedlings. The present study revealed the complexity of the wheat nsLtp gene family and showed that the expression of nsLtp genes is developmentally regulated in the seeds, suggesting a specific function for each of the corresponding proteins.