RESUMO
MAIN CONCLUSION: Identification of PbLTP genes in pear and functional characterization of PbLTP4 in the transport of suberin monomers of russet skin formation. Non-specific lipid-transfer protein (nsLTP) is an abundant and diverse alkaline small molecule protein in the plant kingdom with complex and diverse biophysiological functions, such as transfer of phospholipids, reproductive development, pathogen defence and abiotic stress response. Up to now, only a tiny fraction of nsLTPs have been functionally identified, and the distribution of nsLTPs in pear (Pyrus bretschneideri) (PbLTPs) has not been fully characterized. In this study, the genome-wide analysis of the nsLTP gene family in the pear genome identified 67 PbLTP proteins, which could be divided into six types (1, 2, C, D, E, and G). Similar intron/exon structural patterns were observed in the same type, strongly supporting their close evolutionary relationship. In addition, PbLTP4 was highly expressed in russet pear skin compared with green skin, which was located in the plasma membrane. Coexpression network analysis showed that PbLTP4 closely related to suberin biosynthetic genes. The biological function of PbLTP4 in promoting suberification has been demonstrated by overexpression in Arabidopsis. Identification of suberin monomers showed that PbLTP4 promotes suberification by regulating 9,12-octadecadienoic acid and hexadecanoic acid transport. These results provide helpful insights into the characteristics of PbLTP genes and their biological function in the transport of suberin monomers of russet skin formation.
