Plant grafting relieves asymmetry of jasmonic acid response induced by wounding between scion and rootstock in tomato hypocotyl

Plant grafting is a sequential wound healing process. However, whether wounding induces a different jasmonic acid (JA) response within half a day (12 h) after grafting or non-grafting remains unclear. Using the tomato hypocotyl grafting method, we show that grafting alleviates the asymmetrical accumulation of JA and jasmonic acid isoleucine conjugate (JA-Ile) in scion and rootstock caused by wounding, and from 2 h after tomato micrografting, grafting obviously restored the level of JA-Ile in the scion and rootstock. Meanwhile, five JA-related genes, SlLOX11, SlAOS, SlCOI1, SlLAPA and SlJA2L, are detected and show significant changes in transcriptional expression patterns within 12 h of grafting, from asymmetrical to symmetrical, when the expression of 30 JA- and defense-related genes were analyzed. The results indicated that grafting alleviates the asymmetrical JA and defense response between scion and rootstock of the tomato hypocotyl within 12 h as induced by wounding. Moreover, we demonstrate that in the very early hours after grafting, JA-related genes may be involved in a molecular mechanism that changes asymmetrical expression as induced by wounding between scion and rootstock, thereby promoting wound healing and grafting success.

The disease progression and molecular defense response in Chenopodium quinoa infected with Peronospora variabilis, the causal agent of quinoa downy mildew

The downy mildew disease, caused by the biotrophic oomycete Peronospora variabilis, is the largest environmental threat to quinoa (Chenopodium quinoa Willd.) cultivation in the Andean highlands. However, so far no molecular information on the quinoa-Peronospora interaction has been reported. Here, we have developed tools to study the downy mildew disease in quinoa at gene expression level. Living P. variabilis could be isolated and maintained in the presence of a fungicide, allowing the characterization of downy mildew disease progression in two differently susceptible quinoa cultivars under controlled conditions. Quinoa gene expression changes induced by P. variabilis were analysed by qRT-PCR for quinoa homologues of Arabidopsis thaliana pathogen-associated genes. Overall, we observed a slower disease progression and higher tolerance in the quinoa cultivar Kurmi than in the cultivar Maniquena Real. We also observed that quinoa orthologs of A. thaliana genes involved in the salicylic acid defense response pathway (AtCAT2 and AtEP3) did not have changes in its gene expression. In contrast, quinoa orthologs of A. thaliana gene markers of the induction of the jasmonic acid response pathway (AtWRKY33 and AtHSP90) were significantly induced in plants infected with P. variabilis. These genes could be used as defense response markers to select quinoa cultivars that are more tolerant to P. variabilis infection.