The mechanism of non-cell autonomous movement and its regulation are still unclear, but RNA-binding proteins (RBP) identified from phloem sap of pumpkin bind to mobile mRNAs to regulate their movement [ 2, 20].
Comparisons of the abundance, movement directions and patterns of mobile mRNAs in the in vitro and field grafts revealed an important fact that while many hundreds, perhaps even thousands, of genes could transmit their mRNAs between graft partners, only a small number of them might reach certain tissues to become biologically relevant.
We recognize that our method for estimating transmission rates of mobile mRNAs has certain limits.
Transmission rates of mobile mRNAs could be influenced by genotypes, graft partners, growing conditions and other factors.
Interestingly, a similar percentage (45%%) of mobile mRNAs from the rootstock 'C3309' were also found in the scion 'Riesling' under both growing conditions (Fig. 2b).
Because only a small number of mobile mRNAs were present in the receptor tissue, their biological significances, if any, were difficult to assess.
However, the numbers of mobile mRNAs produced and transmitted by V. girdiana and V. palmata were similar when they served as rootstocks or scions in these grafts (Fig. 2a).
We examined biological significances of the mobile mRNAs detected in the grafts grown in two different pH soil conditions.
As what was observed in the in vitro grafts, some of the mobile mRNAs were transmitted bi-directionally to both scion and rootstock, with three in soil with the pH of 5.5 and five with the pH of 6.5.
