Bioinformatic identification and analyses of the non-specific lipid transfer proteins in wheat

Non-specific lipid transfer proteins (nsLTPs/LTPs) that can transport various phospholipids across the membrane in vitro are widespread in the plant kingdom, and they play important roles in many biological processes that are closely related to plant growth and development. Recently, nsLTPs have been shown to respond to different forms of abiotic stresses. Despite the vital roles of nsLTPs in many plants, little is known about the nsLTPs in wheat. In this study, 330 nsLTP proteins were identified in wheat and they clustered into five types (1, 2, c, d, and g) by phylogenetic analysis with the nsLTPs from maize, Arabidopsis, and rice. The wheat nsLTPs of typed included three subtypes (dl, d2, and d3) and type g included seven subtypes (g1-g7). Genetic structure and motif pattern analyses showed that members of each type had similar structural composition. Moreover, GPI-anchors were found to exist in non-g type members from wheat for the first time. Chromosome mapping revealed that all five types were unevenly and unequally distributed on 21 chromosomes. Furthermore, gene duplication events contributed to the proliferation of the nsLTP genes. Large-scale data mining of RNA-seq data covering multiple growth stages and numerous stress treatments showed that the transcript levels of some of the nsLTP genes could be strongly induced by abiotic stresses, including drought and salinity, indicating their potential roles in mediating the responses of the wheat plants to these abiotic stress conditions. These findings provide comprehensive insights into the nsLTP family members in wheat, and offer candidate nsLTP genes for further studies on their roles in stress resistance and potential for improving wheat breeding programs.