a Stress-Responsive Protein Kinase, Positively Regulates Rice Resistance to via Phytohormone Dynamics.

Plants undergo several but very precise molecular, physiological, and biochemical modulations in response to biotic stresses. Mitogen-activated protein kinase (MAPK) cascades orchestrate multiple cellular processes including plant growth and development as well as plant responses against abiotic and biotic stresses. However, the role of MAPK kinases (MAPKKs/MKKs/MEKs) in the regulation of plant resistance to herbivores has not been extensively investigated. Here, we cloned a rice MKK gene, , and investigated its function. It was observed that mechanical wounding, infestation of brown planthopper (BPH) , and treatment with methyl jasmonate (MeJA) or salicylic acid (SA) could induce the expression of . The over-expression of (oe-MKK3) increased levels of jasmonic acid (JA), jasmonoyl-L-isoleucine (JA-Ile), and abscisic acid (ABA), and decreased SA levels in rice after BPH attack. Additionally, the preference for feeding and oviposition, the hatching rate of BPH eggs, and BPH nymph survival rate were significantly compromised due to over-expression of . Besides, oe-MKK3 also augmented chlorophyll content but impaired plant growth. We confirm that MKK3 plays a pivotal role in the signaling pathway. It is proposed that mediated positive regulation of rice resistance to BPH by means of herbivory-induced phytohormone dynamics.