Abstract
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, OsMKK3, and investigated its function. It was observed that mechanical wounding, infestation of brown planthopper (BPH) Nilaparvata lugens, and treatment with methyl jasmonate (MeJA) or salicylic acid (SA) could induce the expression of OsMKK3. The over-expression of OsMKK3 (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 OsMKK3. 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 OsMKK3 mediated positive regulation of rice resistance to BPH by means of herbivory-induced phytohormone dynamics.
Highlights
In natural ecosystems, plants frequently experience herbivore attacks
Mechanical wounding and salicylic acid (SA) treatments rapidly induced the expression of OsMKK3 to a maximum at 6 hours post treatment and 4 hpt, respectively (Figure 1A,D)
With gravid brown planthopper (BPH) females and methyl jasmonate (MeJA) treatments the expression of this gene was elicited at a later time, reaching a peak at 48 hpt (Figure 1B,C)
Summary
Plants possess complicated defense systems to respond against insect attack and protect themselves. These defense strategies include physical barriers, metabolic adjustments, signaling cascades, and expression of different herbivory-associated genes [1,2,3,4,5]. The process of plant defense involves perception of herbivores, signal transduction, reconfiguration of metabolism, and changes in phenology [6]. Mitogen-activated protein kinase (MAPK) cascades act upstream of hormone-mediated signaling and, pivotal in plant defense responses to herbivores [4,6,15]
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