Genome-wide identification of thaumatin-like protein family in pear and functional analysis their roles in pollen growth

Thaumatin-like proteins (TLPs) are crucial for plant growth and development. However, the function of TLPs in pear pollen tube growth has not been fully elucidated. In this study, we characterized 40 PbrTLPs within the pear (Pyrus bretschneideri) genome and classified them into 10 groups according to their phylogenetic relationships, which exhibited significant similarities in gene structure and conserved motifs within each group. Microcollinearity analysis indicated that recent whole genome duplication (WGD) events significantly contributed to the expansion of the PbrTLP family, with purifying selection predominantly shaping the evolution of PbrTLPs. Transcriptomic data and qRT-PCR analysis revealed tissue-specific expression patterns of PbrTLP members. Notably, PbrTLP36 was identified as a strongly expressed gene in pollen tubes and confirmed to be a secreted protein. Functional assays in pollen tubes and tobacco cells suggested that knockdown the PbrTLP36 expression did not affect pollen tube growth, but the PbrTLP36 protein did confer antimicrobial activity. PbrTLP36 protein could effectively reduce the inhibitory effect of black spot fungi on pollen. The promoter cis-elements of PbrTLPs suggest potential responsiveness to a variety of abiotic and biotic stresses. Functional interaction network analysis suggested that several resistance genes acted synergistically with PbrTLP36. In conclusion, our study characterized the evolutionary pattern of the PbrTLP family and revealed the specific function of PbrTLP36, laying the groundwork for further functional investigations.