Abstract
Non-specific Lipid Transfer Proteins (nsLTPs) are involved in numerous biological processes. To date, only a fraction of wheat (Triticum aestivum L.) nsLTPs (TaLTPs) have been identified, and even fewer have been functionally analysed. In this study, the identification, classification, phylogenetic reconstruction, chromosome distribution, functional annotation and expression profiles of TaLTPs were analysed. 461 putative TaLTPs were identified from the wheat genome and classified into five types (1, 2, C, D and G). Phylogenetic analysis of the TaLTPs along with nsLTPs from Arabidopsis thaliana and rice, showed that all five types were shared across species, however, some type 2 TaLTPs formed wheat-specific clades. Gene duplication analysis indicated that tandem duplications contributed to the expansion of this gene family in wheat. Analysis of RNA sequencing data showed that TaLTPs were expressed in most tissues and stages of wheat development. Further, we refined the expression profile of anther-enriched expressed genes, and identified potential cis-elements regulating their expression specificity. This analysis provides a valuable resource towards elucidating the function of TaLTP family members during wheat development, aids our understanding of the evolution and expansion of the TaLTP gene family and, additionally, provides new information for developing wheat male-sterile lines with application to hybrid breeding.
Highlights
Plant non-specific Lipid Transfer Proteins are small and soluble proteins with the ability to transfer various lipid molecules between membranes in vitro. Non-specific Lipid Transfer Proteins (nsLTPs) are characterized by an eight cysteine motif (8 CM) backbone with the general form C-Xn-C-Xn-CC-Xn-CXC-Xn-C-Xn-C1
Predicted nsLTPs were classified into five types according to Edstam et al.[6] (Type 1, 2, C, D and G); type 2 contained most members with 59.44% of wheat nsLTPs, followed by type G (18.66%), type D (12.36%), type 1 (8.46%) and type C (1.08%)
In comparison to A. thaliana, rice and maize, we found the wheat genome to contain over 5 times the number of nsLTPs (Table 1)
Summary
Plant non-specific Lipid Transfer Proteins (nsLTPs) are small and soluble proteins with the ability to transfer various lipid molecules between membranes in vitro. nsLTPs are characterized by an eight cysteine motif (8 CM) backbone with the general form C-Xn-C-Xn-CC-Xn-CXC-Xn-C-Xn-C1. To A. thaliana nsLTP genes, the maize (Zea mays) Ms44 encodes a type C LTP expressed in tapetal cells with its silencing having no effect on fertility[11]. Silencing of the rice OsC6, an anther-specific LTP, resulted in reduced pollen fertility[12]. Different to what has been observed in rice, wheat TaMs1 is a nsLTP type G, which shows expression in anthers containing pre-meiosis to meiotic microspores[13,14]. We conducted a comprehensive study on the phylogeny, genomic structure, chromosomal location and expression profiles of the nsLTP gene family in wheat. Our analysis provides new insights into the TaLTP gene family which will support future functional research of nsLTPs. We identified anther-enriched nsLTPs of likely involvement in pollen development. When combined with new gene-editing technologies, this opens opportunities for exploring new loci for inducing male sterility that has application to hybrid breeding
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