Non-specific lipid transfer proteins in maize

Background: In plant, non-specific lipid transfer proteins (nsLTPs) are small, basic proteins that have been reported to be involved in numerous biological processes such as transfer of phospholipids, reproductive development, pathogen defence and abiotic stress response. To date, only a tiny fraction of plant nsLTPs have been functionally identified, and even fewer have been identified in maize [Zea mays (Zm)]. Results: In this study, we carried out a genome-wide analysis of nsLTP gene family in maize and identified 63 nsLTP genes, which can be divided into five types (1, 2, C, D and G). Similar intron/exon structural patterns were observed in the same type, strongly supporting their close evolutionary relationship. Gene duplication analysis indicated that both tandem and segmental duplication contribute to the diversification of this gene family. Additionally, the three-dimensional structures of representative nsLTPs were studied with homology modeling to understand their molecular functions. Gene ontology analysis was performed to obtain clues about biological function of the maize nsLTPs (ZmLTPs). The analyses of putative upstream regulatory elements showed both shared and distinct transcriptional regulation motifs of ZmLTPs, further indicating that ZmLTPs may play roles in diverse biological processes. The dynamic expression patterns of ZmLTPs family across the different developmental stages showed that several of them exhibit tissue-specific expression, indicative of their important roles in maize life cycle. Furthermore, we focused on the roles of maize nsLTPs in biotic and abiotic stress responses. Our analyses demonstrated that some ZmLTPs exhibited a delayed expression pattern after the infection of Ustilago maydis and differentially expressed under drought, salt and cold stresses, and these may be a great help for further studies to improve the stress resistance and tolerance in maize breeding. Conclusions: Our results provide new insights into the phylogenetic relationships and characteristic functions of maize nsLTPs and will be useful in studies aimed at revealing the global regulatory network in maize development and stress responses, thereby contributing to the maize molecular breeding with enhanced quality traits.