Genome-wide identification and expression profiling of the PIN auxin transporter gene family in L. chinense

Background: The genus Liriodendron is ancient and contains only two species, L. chinense and L. tulipifera . These two Liriodendron sister species, with a typical intercontinental discontinuous distribution in east Asia ( L. chinense ) and eastern North America ( L. tulipifera ), have great scientific value for paleobotany systematics. L. chinense is now recognized as an endangered species partially due to its low natural settling rate. In order to improve our understanding of how this species develops and grows and contribute to protecting this valuable relict species from extinction, it is necessary to explore the mechanisms underlying organ morphogenesis and embryonic development, in which auxin plays an important role. The auxin efflux carrier PIN-FORMED (PIN) proteins are required for the polar transport of auxin between cells through their asymmetric distribution on the plasma membrane, thus mediating the differential distribution of auxin in plants and, finally, affecting plant growth and developmental processes.ResultsIn this study, 11 PIN genes were identified in the L. chinense genome . The structural characteristics and evolutionary status of LcPIN genes were thoroughly investigated and interpreted combining physicochemical property analysis, evolutionary analysis, gene structure analysis, chromosomal localization, etc. In addition, motif sequences were used to predict possible functional sites. Further qRT-PCR experiments and transcriptome data analysis indicated that LcPIN genes may potentially play an important role during organ development and somatic embryogenesis in Liriodendron . For example, specific expression of LcPIN3 and LcPIN6a at different developmental stages of stamens and petals suggests their involvement in the development of these organs.ConclusionThis study provides a foundation for further genetic and functional analyses of PIN-mediated auxin patterning during organ morphogenesis and embryogenesis in L. chinense .