Characterization of the pectin methylesterase inhibitor gene family in Rosaceae and role of PbrPMEI23/39/41 in methylesterified pectin distribution in pear pollen tube

Main conclusion Pectin methylesterase inhibitor gene family in the seven Rosaceae species (including three pear cultivars) is characterized and three pectin methylesterase inhibitor genes are identified to regulate pollen tube growth in pear. Pectin methylesterase inhibitor (PMEI) participates in a variety of biological processes in plants. However, the information and function of PMEI genes in Rosaceae are largely unknown. In this study, a total of 423 PMEI genes are identified in the genomes of seven Rosaceae species. The PMEI genes in pear are categorized into five subfamilies based on structural analysis and evolutionary analysis. WGD and TD are the main duplication events in the PMEI gene family of pear. Quantitative real-time PCR analysis indicates that PbrPMEI23, PbrPMEI39, and PbrPMEI41 are increasingly expressed during pear pollen tube growth. Under the treatment of recombinant proteins PbrPMEI23, PbrPMEI39 or PbrPMEI41, the content of methylesterified pectin at the region 5-20 mu m from the pollen tube tip significantly increases, and the growth of pear pollen tubes is promoted. These results indicate that PMEI regulates the growth of pollen tubes by changing the distribution of methylesterified pectin in the apex.

Automated summary

This study characterized the pectin methylesterase inhibitor gene family in seven Rosaceae species and identified three genes that regulate pollen tube growth in pear. Quantitative real-time PCR analysis revealed that these genes are increasingly expressed during pear pollen tube growth. The results suggest that pectin methylesterase inhibitor regulates pollen tube growth by changing the distribution of methylesterified pectin in the apex.