The β-1,3-Glucanase Degrades Callose at Plasmodesmata to Facilitate the Transport of the Ribonucleoprotein Complex in Pyrus betulaefolia

Grafting is widely used to improve the stress tolerance and the fruit yield of horticultural crops. Ribonucleoprotein complexes formed by mRNAs and proteins play critical roles in the communication between scions and stocks of grafted plants. In Pyrus betulaefolia, ankyrin was identified previously to promote the long-distance movement of the ribonucleoprotein complex(PbWoxT1-PbPTB3) by facilitating callose degradation at plasmodesmata. However, the mechanism of the ankyrin-mediated callose degradation remains elusive. In this study, we discovered a beta-1,3-glucanase (EC 3.2.1.39, PbPDBG) using ankyrin as a bait from plasmodesmata by co-immunoprecipitation and mass spectrometry. Ankyrin was required for the plasmodesmata-localization of PbPDBG. The grafting and bombardment experiments indicated that overexpressing PbPDBG resulted in decreased callose content at plasmodesmata, and thereby promoting the long-distance transport of the ribonucleoprotein complex. Altogether, our findings revealed that PbPDBG was the key factor in ankyrin-mediated callose degradation at plasmodesmata.

Automated summary

Grafting is commonly used to enhance stress tolerance and fruit yield in horticultural crops. Ribonucleoprotein complexes consisting of mRNAs and proteins play crucial roles in communication between scions and stocks in grafted plants. This study identified a beta-1,3-glucanase (PbPDBG) that facilitates ankyrin-mediated callose degradation at plasmodesmata, promoting long-distance transport of ribonucleoprotein complexes. These findings underscore the importance of PbPDBG in ankyrin-mediated callose degradation.