Anther Dehiscence Disturbed by High Temperature and Water Stress Presented in Os DIR Gene Expression in Rice(Oryza sativa L.)

In future climates, rice could more frequently be subjected to simultaneous high temperature(HT) and water stress(WS) during sensitive developmental stages such as flowering. In this study, two rice genotypes were exposed to HT, WS and combined high temperature and water stress(WS + HT) during flowering to quantify their response through anther dehiscence. Gene expression profiles of 15 selected Os DIRs revealed differences among stresses and between varieties. The targeted gene Os DIR-08, which was considered to be a HT stress candidate gene, was decreasingly expressed from the 1st d to the 4th d under HT stress in Nagina 22(N22) while increased in Moroberekan. Varies of the expression of Os DIR genes in stresses intuitively reflects on the lignin-staining at the anther dehisced sites, which implied a negative relationship between the lignin biosynthesis and Os DIRs' expression. Anther dehiscence disturbed by HT and WS + HT stress showed a negative cumulative effect in HT sensitive variety Moroberekan but not in N22. Higher level of anther dehiscence in N22 under HT and WS + HT stress indicated its true tolerance of HT and to WS + HT during anthesis. The differentially expressed of Os DIR(s) under various managed stresses caused the difference of the lignin-staining at the anther dehisced site in N22, and thus transformed anther dehiscence correspondingly might be one of the main reasons for the tolerance.

Balancing selection and wild gene pool contribute to resistance in global rice germplasm against planthopper

Interactions and co-evolution between plants and herbivorous insects are critically important in agriculture.Brown planthopper(BPH)is the most severe insect of rice,and the biotypes adapt to feed on different rice genotypes.Here,we present genomics analyses on 1,520 global rice germplasms for resistance to three BPH biotypes.Genome-wide association studies identified 3,502 single nucleotide polymorphisms(SNPs)and 59 loci associated with BPH resistance in rice.We cloned a previously unidentified gene Bph37 that confers resistance to BPH.The associated loci showed high nucleotide diversity.Genome-wide scans for trans-species polymorphisms revealed ancient balancing selection at the loci.The secondarily evolved insect biotypes II and III exhibited significantly higher virulence and overcame more rice varieties than the primary biotype I.In response,more SNPs and loci evolved in rice for resistance to biotypes II and III.Notably,three exceptional large regions with high SNP density and resistance-associated loci on chromosomes 4 and 6 appear distinct between the resistant and susceptible rice varieties.Surprisingly,these regions in resistant rice might have been retained from wild species Oryza nivara.Our findings expand the understanding of long-term interactions between rice and BPH and provide resistance genes and germplasm resources for breeding durable BPH-resistant rice varieties.

Lipidomic analyses reveal enhanced lipolysis in planthoppers feeding on resistant host plants

The brown planthopper(BPH)(Nilaparvata lugens St?l)is a highly destructive pest that seriously damages rice(Oryza sativa L.)and causes severe yield losses.To better understand the physiological and metabolic mechanisms through which BPHs respond to resistant rice,we combined mass-spectrometry-based lipidomics with transcriptomic analysis and gene knockdown techniques to compare the lipidomes of BPHs feeding on either of the two resistant(NIL-Bph6 and NIL-Bph9)plants or a wild-type,BPH susceptible(9311)plant.Insects that were fed on resistant rice transformed triglyceride(TG)to phosphatidylcholine(PC)and digalactosyldiacylglycerol(DGDG),with these lipid classes showing significant alterations in fatty acid composition.Moreover,the insects that were fed on resistant rice were characterized by prominent expression changes in genes involved in lipid metabolism processes.Knockdown of the NlBmm gene,which encodes a lipase that regulates the mobilization of lipid reserves,significantly increased TG content and feeding performance of BPHs on resistant plants relative to dsGFP-injected BPHs.Our study provides the first detailed description of lipid changes in BPHs fed on resistant and susceptible rice genotypes.Results from BPHs fed on resistant rice plants reveal that these insects can accelerate TG mobilization to provide energy for cell proliferation,body maintenance,growth and oviposition.