Messenger RNAs Mobile in Salix Matsudana Grafts Were in Association With Plant Rooting

Abstract Messenger RNAs exchanged between scions and rootstocks of grafted plants seriously affect their traits performance. The study goals were to identify the long-distance mRNA transmission events in grafted willows using a transcriptome analysis and to reveal the possible effects on rooting traits. The results showed that the Salix matsudana variety 9901 has better rooting ability than YJ, which reasonably improved the rooting performance of the heterologous grafts 9901 (scion) / YJ (rootstock). A transcriptome analysis showed that 2,948 differentially expressed genes (DEGs) were present in the rootstock of 9901/YJ grafted plants in comparison with YJ/YJ. Among them, 692 were identified as mRNAs moved from 9901 scion based on a SNP analysis of two parents. They were mostly 1,001–1,500 bp, had 40–45% GC contents, or had expression abundance values less than 10. However, mRNAs over 4,001 bp, having 50–55% GC contents, or having expression abundance values of 10–20 were preferentially transferred. Eight mRNAs subjected to long-distance trafficking were involved in the plant hormone pathways and may significantly promote the root growth of grafted plants. Thus, heterologous grafts of Salix matsudana could efficiently influence plant rooting since of the mRNAs transport from scion to rootstock. Thus, the grafting parents and grafting patterns would be much concerned in the breeding process to gain the expected results in future.