Integrating Iso-seq and RNA-seq analyses to unveil bidirectional movement of mRNAs in oil-Camellia heterografting

Grafting has long been the primary technical method for breeding oil-Camellia varieties and improving crop performance. This is a major factor limiting Camellia oil yield. mRNAs are key signaling molecules involved in stock-scion interactions. Although grafting is traditionally considered a form of asexual reproduction, it can induce phenotypic variations that are potentially driven by genetic material transfer and epigenetic regulation. However, little is known about the role of mRNA movement between rootstocks and scions in heterografting. In this study, we investigated mobile mRNAs involved in heterografting between Camellia oleifera and Camellia chekiangoleosa using third-generation full-length transcriptome sequencing (Iso-seq) and second-generation transcriptome sequencing (RNA-seq) analyses. Bidirectional movement of mRNAs was observed after grafting, and these mobile mRNAs were significantly enriched in pathways related to plant hormone signal transduction and auxin biosynthesis. To validate the mRNA movement events, heterografting experiments were conducted between transgenic Xiangyan No. 7 (harboring the key genes GH3 and UGT involved in hormone signaling and auxin biosynthesis) and wild-type Nicotiana × sanderae. The results confirmed bidirectional mRNA movement, with the transferred mRNAs remaining functional in the recipient cells. These findings elucidate the critical mechanisms of rootstock-scion interaction in oil-Camellia heterografting, highlighting mRNA mobility as a regulatory factor in genetic information exchange. This study advances our understanding of grafting biology and provides a foundation for novel grafting-based strategies to enhance crop breeding and yield.