Evolution, expression analysis, and functional verification of Catharanthus roseus RLK1-like kinase (CrRLK1L) family proteins in pear (Pyrus bretchneideri)

The Catharanthus roseus RLK1-like kinase (CrRLK1L) family is involved in multiple processes during plant growth. However, little is known about CrRLK1L in the wood of the pear fruit tree Pyrus bretchneideri. In this study, 26 CrRLK1L gene members were identified in pear and were grouped into six subfamilies according to phylogenetic analyses. Evolutionary analysis indicated that recent whole genome duplication (WGD) and dispersed gene duplications may contribute to the expansion of the CrRLK1L gene family in pear. Moreover, tissue-specific expression analyses suggested that CrRLK1Ls are involved in the development of various pear tissues. Subsequent qRT-PCR analyses indicated that CrRLK1Ls might play important roles in pollen tube growth. Finally, experiments with antisense oligonucleotides (ASO) demonstrated that PbrCrRLK1L26 have functions in pollen tube elongation and that PbrCrRLK1L3 regulates pollen tube rupture. These results will be useful for elaborating the biological roles of CrRLK1Ls in pear growth and development.