Effects Of MiR319a On Tomato Growth And Development And Response To Root-knot Nematodes

Tomato(Solanum lycopersicum) occupies an important position in our vegetable production. However, root knot nematodes (RKN) disease generally occurs because of planting structure changes and continuous cropping. Currently, RKN disease is one of the most serious diseases in tomato production, and it results huge economic losses to tomato cultivation and production. Thus, to improve the tomato resistance to RKN become a problem to be solved urgently in agricultural production. Recently, it has been reported that microRNAs’roles have been characterized in the processes underlying diverse aspects of plant development and in response to different stresses. Therefore, we have a study that the effects of miR319a on tomato development and the response of tomato to RKN.This study investigated the role of miR319a in tomato development and in response to root knot nematode (Meloidogyne graminicola) stress using transgenic tomatoes (Solanum lycopersicum) overexpressing the miR319a gene and the miR319-target LANCEOLATE(LA) gene which is co-segregation with SITCP4 and contains a mutation in the LA miRNA-binding site complementary to the miR319a, a miR319-resistant version of LA. We found that the growth and development of tomato plants overexpressing miR319a (FIL＞＞miR319a) were significantly affected, such as stunted growth, jagged and wavy leaves, capreolary petals and some changes in trichome density. In addition, the number of root nodules in FIL＞＞miR319a was greater than that in overexpressing LA plants (FIL＞＞LAm 45 days after inoculation with RKN. The gene expression analysis revealed significant differences in the expression patterns of LOXD, AOSl, AOCl and OPR3 involved in jasmonic acid (JA) biosynthesis between WT and transgenic tomato plants (FIL＞＞miR319a and FIL＞＞LA) at different time points after inoculation with RKN. These genes were down-regulated in FIL＞＞miR319a and up-regulated in FIL＞＞LAm plants. We detected the endogenous JA content in WT and transgenic tomatoes at Oh and 12h after inoculation. The result demonstrated that the JA content was lowest and did not change at 12h after inoculation in FIL＞＞miR319a plants. Whereas, it was the highest in FIL＞＞Am plants, reaching approximately 3 fold in WT at 12h after inoculation. In addtion, the LA protein could inhibit the expression of JAZ3 which is negative regulator in JA signaling pathways. These results indicated that overexpressing miR319a not only affected tomato development but also reduced tomato’s resistance to RKN infection through regulating the JA biosynthetic and signaling pathways.