Honeydew-associated microbes elicit defense responses against brown planthopper in rice

Feeding of sucking insects, such as the rice brown planthopper (Nilaparvata lugens; BPH), causes only limited mechanical damage on plants that is otherwise essential for injury-triggered defense responses against herbivores. In pursuit of complementary BPH elicitors perceived by plants, we examined the potential effects of BPH honeydew secretions on the BPH monocot host, rice (Oryza sativa). We found that BPH honeydew strongly elicits direct and putative indirect defenses in rice, namely accumulation of phytoalexins in the leaves, and release of volatile organic compounds from the leaves that serve to attract natural enemies of herbivores, respectively. We then examined the elicitor active components in the honeydew and found that bacteria in the secretions are responsible for the activation of plant defense. Corroborating the importance of honeydew-associated microbiota for induced plant resistance, BPHs partially devoid of their microbiota via prolonged antibiotics ingestion induced significantly less defense in rice relative to antibiotic-free insects applied to similar groups of plants. Our data suggest that rice plants may additionally perceive herbivores via their honeydew-associated microbes, allowing them to discriminate between incompatible herbivores—that do not produce honeydew—and those that are compatible and therefore dangerous

Comparative analysis of sorghum (C4) and rice (C3) plant headspace volatiles induced by artificial herbivory

Acute stress responses include release of defensive volatiles from herbivore-attacked plants. Here we used two closely related monocot species, rice as a representative C3 plant, and sorghum as a representative C4 plant, and compared their basal and stress-induced headspace volatile organic compounds (VOCs). Although both plants emitted similar types of constitutive and induced VOCs, in agreement with the close phylogenetic relationship of the species, several mono- and sesquiterpenes have been significantly less abundant in headspace of sorghum relative to rice. Furthermore, in spite of generally lower VOC levels, some compounds, such as the green leaf volatile (Z)-3-hexenyl acetate and homoterpene DMNT, remained relatively high in the sorghum headspace, suggesting that a separate mechanism for dispersal of these compounds may have evolved in this plant. Finally, a variable amount of several VOCs among three sorghum cultivars of different geographical origins suggested that release of VOCs could be used as a valuable resource for the increase of sorghum resistance against herbivores

Direct and indirect defense mechanism reveal complex protective shield against insect herbivores in rice

Plants evolved effective defense strategies against herbivores that depend on rapid and reliable recognition of herbivore attack, and subsequent induction of appropriate plant defenses. Two major defense strategies in plants involve direct and indirect defense mechanisms. Our group is using two crops, rice and sorghum, to understand their innate defense mechanisms against naturally occurring insect herbivores. For example, we could already show that herbivore feeding in rice elicits proteinase inhibitors, phenolamide (PA) accumulation and momilactones as part of its direct defense; however, many more metabolites against insects in rice can be predicted from our results of non-targeted metabolomics analyses. So far, we studied in detail and report here the role of two major rice PA conjugates, p-coumaroylputrescine (CoP) and feruloylputrescine (FP). Both compounds are strongly induced by chewing and sucking herbivore feeding. In bioassays with synthetic CoP and FP, mortality of rice sucking pest, brown planthopper (Nilaparvata lugens), was enhanced by addition of CoP or FP to artificial diet at 100 µg/ml concentrations. However, chewing herbivore survival was not affected, leaving the importance of these compounds against chewing herbivores in question. Next, we identified genetic basis for phenolamide accumulation in rice by cloning the key biosynthetic genes. We show that phenolamides and their genes are expressed in tissue specific, as well as inducible manner in rice. While main constitutive gene expression and metabolite accumulation occurred in field-grown roots and panicles of rice, herbivores and mechanical wounding induced additional expression and accumulation of CoP and FP in the treated leaves. The accumulation patterns and wide distribution of phenolamides in plant kingdom suggested rapid evolution as well as multiple functions of these metabolites, especially during plant interactions with other organisms. In indirect defense, we report that herbivory elicits emissions of several volatile organic compounds in rice, dominated by monoterpene linalool, in insect species-dependent patterns. A generalist herbivore tended to provoke stronger responses in rice compared to its specialized insect pest. We hypothesize that such differential response lays in differential composition of oral secretions (and elicitor contents) as well as typical feeding behavior of generalist and specialist insects on rice plants. We also show that volatiles are emitted in diurnally specific patterns, suggesting differential way of communication between plants and insects during light and dark periods. We speculate that this might be an adaptation of plants to herbivore lifestyles, which are either nocturnal or active during the daylight, allowing plants to boost or relax their defense systems during diurnal cycle.status: publishe

Honeydew-associated microbes elicit defense responses against brown planthopper in rice

Feeding of sucking insects, such as the rice brown planthopper (Nilaparvata lugens; BPH), causes only limited mechanical damage on plants that is otherwise essential for injury-triggered defense responses against herbivores. In pursuit of complementary BPH elicitors perceived by plants, we examined the potential effects of BPH honeydew secretions on the BPH monocot host, rice (Oryza sativa). We found that BPH honeydew strongly elicits direct and putative indirect defenses in rice, namely accumulation of phytoalexins in the leaves, and release of volatile organic compounds from the leaves that serve to attract natural enemies of herbivores, respectively. We then examined the elicitor active components in the honeydew and found that bacteria in the secretions are responsible for the activation of plant defense. Corroborating the importance of honeydew-associated microbiota for induced plant resistance, BPHs partially devoid of their microbiota via prolonged antibiotics ingestion induced significantly less defense in rice relative to antibiotic-free insects applied to similar groups of plants. Our data suggest that rice plants may additionally perceive herbivores via their honeydew-associated microbes, allowing them to discriminate between incompatible herbivores—that do not produce honeydew—and those that are compatible and therefore dangerous

The king and us: representations of monarchy in Thailand and the case of ‘Anna and the King’

In 1998, 20th Century Fox approached the Thai government asking permission to shoot on location in Thailand a film titled Anna and the King, a dramatized version of the famous 1950s musical The King and I. The latter film has long been banned in Thailand. Fox’s plans to produce a new version created a storm of controversy in Thailand, ending in the National Film Board’s decision not to allow the film to be made in Thailand. The completed film (shot in Malaysia) was also eventually banned from Thai movie screens. This article looks at why the story of Anna Leonowens and King Mongkut remains so controversial in Thailand, even in this era of greatly increased media freedom. The article also examines the continued importance of the idea of monarchy to the modern Thai state, and the endless flood of royal imagery that saturates the Thai media and public life generally