Pyramiding of tea Dihydroflavonol reductase and Anthocyanidin reductase increases flavan-3-ols and improves protective ability under stress conditions in tobacco

Integrated transcriptomics and metabolomics analysis provide insight into the resistance response of rice against brown planthopper

Introduction

The brown planthopper (Nilaparvata lugens Stål, BPH) is one of the most economically significant pests of rice. The Bph30 gene has been successfully cloned and conferred rice with broad-spectrum resistance to BPH. However, the molecular mechanisms by which Bph30 enhances resistance to BPH remain poorly understood.

Methods

Here, we conducted a transcriptomic and metabolomic analysis of Bph30-transgenic (BPH30T) and BPH-susceptible Nipponbare plants to elucidate the response of Bph30 to BPH infestation.

Results

Transcriptomic analyses revealed that the pathway of plant hormone signal transduction enriched exclusively in Nipponbare, and the greatest number of differentially expressed genes (DEGs) were involved in indole 3-acetic acid (IAA) signal transduction. Analysis of differentially accumulated metabolites (DAMs) revealed that DAMs involved in the amino acids and derivatives category were down-regulated in BPH30T plants following BPH feeding, and the great majority of DAMs in flavonoids category displayed the trend of increasing in BPH30T plants; the opposite pattern was observed in Nipponbare plants. Combined transcriptomics and metabolomics analysis revealed that the pathways of amino acids biosynthesis, plant hormone signal transduction, phenylpropanoid biosynthesis and flavonoid biosynthesis were enriched. The content of IAA significantly decreased in BPH30T plants following BPH feeding, and the content of IAA remained unchanged in Nipponbare. The exogenous application of IAA weakened the BPH resistance conferred by Bph30.

Discussion

Our results indicated that Bph30 might coordinate the movement of primary and secondary metabolites and hormones in plants via the shikimate pathway to enhance the resistance of rice to BPH. Our results have important reference significance for the resistance mechanisms analysis and the efficient utilization of major BPH-resistance genes.

Enhancing alfalfa resistance to Spodoptera herbivory by sequestering microRNA396 expression

KEY MESSAGE

Sequestering microRNA396 by overexpression of MIM396 enhanced alfalfa resistance to Spodoptera litura larvae, which may be due to increased lignin content and enhanced low-molecular weight flavonoids and glucosinolates biosynthesis. Alfalfa (Medicago sativa), the most important leguminous forage crop, suffers from the outbreak of defoliator insects, especially Spodoptera litura, resulting in heavy losses in yield and forage quality. Here, we found that the expression of alfalfa microRNA396 (miR396) precursor genes and mature miR396 was significantly up-regulated in wounding treatment that simulates feeding injury by defoliator insects. To verify the function of miR396 in alfalfa resistance to insect, we generated MIM396 transgenic alfalfa plants with significantly down-regulated miR396 expression by Agrobacterium-mediated genetic transformation. The MIM396 transgenic alfalfa plants exhibited improved resistance to Spodoptera litura larvae with increased lignin content but decreased JA accumulation. Most of the miR396 putative target GRF genes were up-regulated in MIM396 transgenic lines, and responded to the wounding treatment. By RNA sequencing analysis, we found that the differentially expressed genes related to insect resistance between WT and MIM396 transgenic plants mainly clustered in biosynthesis pathways in lignin, flavonoids and glucosinolates. In addition to the phenotype of enhanced insect resistance, MIM396 transgenic plants also displayed reduced biomass yield and forage quality. Our results broaden the function of miR396 in alfalfa and provide genetic resources for studying alfalfa insect resistance.

Transcriptome and Metabolome Profiling Reveal the Resistance Mechanisms of Rice against Brown Planthopper

Brown planthopper (Nilaparvata lugens Stål, BPH) is one of the most destructive insects affecting rice production. To better understand the physiological mechanisms of how rice responds to BPH feeding, we analyzed BPH-induced transcriptomic and metabolic changes in leaf sheaths of both BPH-susceptible and -resistant rice varieties. Our results demonstrated that the resistant rice reduced the settling, feeding and growth of BPH. Metabolic analyses indicated that BPH infestation caused more drastic overall metabolic changes in the susceptible variety than the resistant rice. Differently accumulated metabolites (DAMs) belonging to flavonoids were downregulated in the susceptible rice but upregulated in resistant variety. Transcriptomic analyses revealed more differentially expressed genes (DEGs) in susceptible rice than resistant rice, and DEGs related to stimulus were significantly upregulated in resistant rice but downregulated in susceptible rice. Combined analyses of transcriptome and metabolome showed that many DEGs and DAMs were enriched in phenylpropane biosynthesis, flavonoid biosynthesis, and plant hormone signal transduction. We conducted correlation analyses of DEGs and DAMs in these pathways and found a high correlation between DEGs and DAMs. Then, we found that the contents of endogenous indole 3-acetic acid (IAA) in resistant rice was lower than that of susceptible rice after BPH feeding, while the salicylic acid (SA) content was the opposite. For functional analysis, an exogenous application of IAA decreased rice resistance to BPH, but the exogenous application of SA increased resistance. In addition, biochemical assessment and quantitative PCR analysis showed that the lignin content of resistant accession was constitutively higher than in susceptible accession. By adding epigallocatechin, the substrate of anthocyanidin reductase (ANR), to the artificial diet decreased the performance of BPH. We first combined a transcriptome-metabolome-wide association study (TMWAS) on rice resistance to BPH in this study. We demonstrated that rice promoted resistance to BPH by inducing epigallocatechin and decreasing IAA. These findings provided useful transcriptomic and metabolic information for understanding the rice-BPH interactions.