Molecular Evidence Of MiR319 Transportation Between Scion And Rootstock And Identification Method Of Tomato Root Knot Nematodes

MicroRNA319 （miR319） is associated with plant development. Its target gene is TCPs transcription factor. The balance between them controls the fate of plant organ growth such as leaves and flowers. What is more, it is involved in regulating part of hormone biosynthesis and signal transduction pathways. Thus, it played a key biochemical function in plant leaf development. However, its mobility has not been demonstrated. By performing micro-grafting experiments using the wild type M82-D and miR319 overexpression tomato line FIL>>319, we further show that grafted plants, M82-D as rootstock while FIL>>319 as scion, constitutively over-expressing miR319 in the shoot accumulate mature miR319 species to a higher level in their wild-type roots than in auto-graft wild-type roots, while corresponding primary transcripts are virtually absent in roots, demonstrating shoot-to-root transport. We demonstrate here that miR319 is a potential graft transmissible signal in tomato （Solanum lycopersicum）. The experiment also found that sly-miR159, sly-miR482d-5 p, novel mir 829 and novel_mir₁019 miRNAs may participate in exchange of information between grafted scion and stock.In this study, each stage of the structural development of graft union formation in tomato plants was examined 3,5,8,11 and 14 days after grafting （DAG） with SEM and a paraffin section technique. Paraffin section images of the transection revealed that parenchymal cells from the graft interface divided and proliferated in most combinations and that cells could be detected at various stages of development. The SEM images of the scion-rootstock longitudinal sections showed that many interconnecting structures appeared at 8 DAG, followed by a vascular rearrangement but did not connect the scion and rootstock. At the next stage, vascular bundle bridges appeared at 11 DAG and connected the scion and rootstock.To better understand JA-mediated nematode resistance, we injected about 3,000 heads of second-stage juveniles of RKN into CM （WT）, JA biosynthetic mutant （spr2） and JA overexpressed transgenic tomato line 35S::prosystemin （35S::PS）. The average root nodules per hill were compared after 50 days inoculation. The number of root nodules by RKN infection of spr2 roots was obviously greater than that in CM roots whereas there were fewer root nodules in 35S::PS roots. spr2 received a foliar application of 0.5 mM MeJA immediately after inoculation with RKN and the number of root nodules was slightly less than that in the spr2 line without exougenous MeJA. The results indicated that the observed effects of both endogenous and exogenous JA on RKN resistance were involved in the JA pathway. To investigate whether resistance to nematodes is related to the expression of defense-related genes in the JA pathway, the expression profiles of 14 systemin/JA-related genes were evaluated by quantitative real-time PCR profiling. It showed that most system element/JA synthesis related gene expression has a tendency to rise in 6-24 h, but back to the basic level after 24 h.