SUMMARYThe jasmonic acid (JA) pathway plays a central role in plant defense responses against insects. Some phloemfeeding insects also induce the salicylic acid (SA) pathway, thereby suppressing the plant's JA response. These phenomena have been well studied in dicotyledonous plants, but little is known about them in monocotyledons. We cloned a chloroplast-localized type 2 13-lipoxygenase gene of rice, OsHI-LOX, whose transcripts were up-regulated in response to feeding by the rice striped stem borer (SSB) Chilo suppressalis and the rice brown planthopper (BPH) Niaparvata lugens, as well as by mechanical wounding and treatment with JA. Antisense expression of OsHI-LOX (as-lox) reduced SSB-or BPH-induced JA and trypsin protease inhibitor (TrypPI) levels, improved the larval performance of SBB as well as that of the rice leaf folder (LF) Cnaphalocrocis medinalis, and increased the damage caused by SSB and LF larvae. In contrast, BPH, a phloem-feeding herbivore, showed a preference for settling and ovipositing on WT plants, on which they consumed more and survived better than on as-lox plants. The enhanced resistance of as-lox plants to BPH infestation correlated with higher levels of BPH-induced H 2 O 2 and SA, as well as with increased hypersensitive response-like cell death. These results imply that OsHI-LOX is involved in herbivore-induced JA biosynthesis, and plays contrasting roles in controlling rice resistance to chewing and phloem-feeding herbivores. The observation that suppression of JA activity results in increased resistance to an insect indicates that revision of the generalized plant defense models in monocotyledons is required, and may help develop novel strategies to protect rice against insect pests.

Crop breeding aims to balance disease resistance with yield; however, single resistance (R) genes can lead to resistance breakdown, and R gene pyramiding may affect growth fitness. Here we report that the rice locus contains a cluster of genes encoding nucleotide-binding leucine-rich repeat (NLR) receptors that confer durable resistance to the fungus without yield penalty. Among these NLR receptors, PigmR confers broad-spectrum resistance, whereas PigmS competitively attenuates PigmR homodimerization to suppress resistance. expression, and thus-mediated resistance, are subjected to tight epigenetic regulation. increases seed production to counteract the yield cost induced by Therefore, our study reveals a mechanism balancing high disease resistance and yield through epigenetic regulation of paired antagonistic NLR receptors, providing a tool to develop elite crop varieties.

The recessive tall rice (Oryza sativa) mutant elongated uppermost internode (eui) is morphologically normal until its final internode elongates drastically at the heading stage. The stage-specific developmental effect of the eui mutation has been used in the breeding of hybrid rice to improve the performance of heading in male sterile cultivars. We found that the eui mutant accumulated exceptionally large amounts of biologically active gibberellins (GAs) in the uppermost internode. Mapbased cloning revealed that the Eui gene encodes a previously uncharacterized cytochrome P450 monooxygenase, CYP714D1. Using heterologous expression in yeast, we found that EUI catalyzed 16a,17-epoxidation of non-13-hydroxylated GAs. Consistent with the tall and dwarfed phenotypes of the eui mutant and Eui-overexpressing transgenic plants, respectively, 16a,17-epoxidation reduced the biological activity of GA 4 in rice, demonstrating that EUI functions as a GAdeactivating enzyme. Expression of Eui appeared tightly regulated during plant development, in agreement with the stagespecific eui phenotypes. These results indicate the existence of an unrecognized pathway for GA deactivation by EUI during the growth of wild-type internodes. The identification of Eui as a GA catabolism gene provides additional evidence that the GA metabolism pathway is a useful target for increasing the agronomic value of crops.

The detrimental effects of global warming on crop productivity threaten to reduce the world's food supply. Although plant responses to changes in temperature have been studied, genetic modification of crops to improve thermotolerance has had little success to date. Here we demonstrate that overexpression of the Arabidopsis thaliana receptor-like kinase ERECTA (ER) in Arabidopsis, rice and tomato confers thermotolerance independent of water loss and that Arabidopsis er mutants are hypersensitive to heat. A loss-of-function mutation of a rice ER homolog and reduced expression of a tomato ER allele decreased thermotolerance of both species. Transgenic tomato and rice lines overexpressing Arabidopsis ER showed improved heat tolerance in the greenhouse and in field tests at multiple locations in China during several seasons. Moreover, ER-overexpressing transgenic Arabidopsis, tomato and rice plants had increased biomass. Our findings could contribute to engineering or breeding thermotolerant crops with no growth penalty.

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.