The roles of jasmonate signalling in nitrogen uptake and allocation in rice (Oryza sativa L.)

Herbivore damage by chewing insects activates jasmonate (JA) signalling that can elicit systemic defense responses in rice. Few details are known, however, concerning the mechanism, whereby JA signalling modulates nutrient status in rice in response to herbivory. (¹⁵ NH₄ )₂ SO₄ labelling experiments, proteomic surveys, and RT-qPCR analyses were used to identify the roles of JA signalling in nitrogen (N) uptake and allocation in rice plants. Exogenous applications of methyl jasmonate (MeJA) to rice seedlings led to significantly reduced N uptake in roots and reduced translocation of recently-absorbed ¹⁵ N from roots to leaves, likely occurring as a result of down-regulation of glutamine synthetase cytosolic isozyme 1-2 and ferredoxin-nitrite reductase. Shoot MeJA treatment resulted in a remobilization of endogenous unlabelled ¹⁴ N from leaves to roots, and root MeJA treatment also increased ¹⁴ N accumulation in roots but did not affect ¹⁴ N accumulation in leaves of rice. Additionally, proteomic and RT-qPCR experiments showed that JA-mediated plastid disassembly and dehydrogenases GDH2 up-regulation contribute to N release in leaves to support production of defensive proteins/compounds under N-limited condition. Collectively, our results indicate that JA signalling mediates large-scale systemic changes in N uptake and allocation in rice plants.