SUMMARYAs important signal molecules, jasmonates (JAs) and green leaf volatiles (GLVs) play diverse roles in plant defense responses against insect pests and pathogens. However, how plants employ their specific defense responses by modulating the levels of JA and GLVs remains unclear. Here, we describe identification of a role for the rice HPL3 gene, which encodes a hydroperoxide lyase (HPL), OsHPL3/CYP74B2, in mediating plantspecific defense responses. The loss-of-function mutant hpl3-1 produced disease-resembling lesions spreading through the whole leaves. A biochemical assay revealed that OsHPL3 possesses intrinsic HPL activity, hydrolyzing hydroperoxylinolenic acid to produce GLVs. The hpl3-1 plants exhibited enhanced induction of JA, trypsin proteinase inhibitors and other volatiles, but decreased levels of GLVs including (Z)-3-hexen-1-ol. OsHPL3 positively modulates resistance to the rice brown planthopper [BPH, Nilaparvata lugens (Stå l)] but negatively modulates resistance to the rice striped stem borer [SSB, Chilo suppressalis (Walker)]. Moreover, hpl3-1 plants were more attractive to a BPH egg parasitoid, Anagrus nilaparvatae, than the wild-type, most likely as a result of increased release of BPH-induced volatiles. Interestingly, hpl3-1 plants also showed increased resistance to bacterial blight (Xanthomonas oryzae pv. oryzae). Collectively, these results indicate that OsHPL3, by affecting the levels of JA, GLVs and other volatiles, modulates rice-specific defense responses against different invaders.

Summary Identification of seed development regulatory genes is the key for the genetic improvement in rice grain quality. NF ‐Ys are the important transcription factors, but their roles in rice grain quality control and the underlying molecular mechanism remain largely unknown. Here, we report the functional characterization a rice NF ‐Y heterotrimer complex NF ‐ YB 1‐ YC 12‐ bHLH 144, which is formed by the binding of NF ‐ YB 1 to NF ‐ YC 12 and then bHLH 144 in a sequential order. Knock‐out of each of the complex genes resulted in alteration of grain qualities in all the mutants as well as reduced grain size in crnf‐yb1 and crnf‐yc12 . RNA ‐seq analysis identified 1496 genes that were commonly regulated by NF ‐ YB 1 and NF ‐ YC 12 , including the key granule‐bound starch synthase gene Wx . NF ‐ YC 12 and bHLH 144 maintain NF ‐ YB 1 stability from the degradation mediated by ubiquitin/26S proteasome, while NF ‐ YB 1 directly binds to the ‘G‐box’ domain of Wx promoter and activates Wx transcription, hence to regulate rice grain quality. Finally, we revealed a novel grain quality regulatory pathway controlled by NF ‐ YB 1‐ YC 12‐ bHLH 144 complex, which has great potential for rice genetic improvement.