The biosynthesis of alarm pheromone in the wheat aphid Rhopalosiphum padi is regulated by hormones via fatty acid metabolism

Aphids are major insect pests in agriculture and forestry worldwide.Following attacks by natural enemies,many aphids release an alarm pheromone to protect their population.In most aphids,the main component of the aphid alarm pheromone(AAP)is the sesquiterpene hydrocarbon(E)-β-farnesene(EβF).However,the mechanisms behind its biosynthesis and regulation remain poorly understood.In this study,we used the bird cherry–oat aphid Rhopalosiphum padi,which is an important wheat aphid,to investigate the regulatory mechanisms of EβF biosynthesis.Our results showed that EβF biosynthesis occurs during the mature embryo period and the molting period of the 1st-and 2nd-instar nymphs.Triglycerides provide the prerequisite material for EβF production and release.Based on transcriptome sequencing,RNAi analysis,hormone treatments,and quantitative measurements,we found that the biosynthesis of EβF utilizes acetyl coenzyme A produced from fatty acid degradation,which can be suppressed by juvenile hormone but it is promoted by 20-hydroxyecdysone through the modulation of fatty acid metabolism.This is the first systemic study on the modulation of EβF production in aphids.The results of our study provide insights into the molecular regulatory mechanisms of AAP biosynthesis,as well as valuable information for designing potential aphid control strategies.

Construction of Plant Antisense Expression Vector with Defective in Anther Dehiscence1 Gene Fragment of Chinese Kale

A pair of primers was designed according to the reported conserved sequence of the defective in anther dehiscencel （DAD1） gene ofArabidopsis thaliana and Brassica rapa. A 558 bp long fragment was amplified from genomic DNA of Chinese kale, showing more than 88% identity with the known DAD1 nucleotide sequence and no intron. The reverse of the amplified fragment was ligated to the downstream of the CaMV35S promoter in the plant expression vector pBIl21. Antisense expression vector pBII21-DAD1F was constructed with DAD1 fragment of Chinese kale, and was transferred into Agrobacterium tumefaciens, which will be used in the transformation to create male sterile materials of Chinese kale.

Identification of heat-induced proteomes in meiotic pollen mother cells of tomato'Maxifort'using single-cell-type tandem mass tag(TMT)proteomics

Heat stress(HS)poses a significant challenge to tomato production due to disruption of the reproductive organs,especially the male gametophytes.This study reports HS-induced proteome changes in meiotic pollen mother cells during early stages of anther development.Tomato(Solanum lycopersicum L.×S.habrochaites)'Maxifort'were grown in a heated polytunnel in Nashville,Tennessee,USA.Plants at flowering stage were subjected to heat treatment at 40±2℃ for 4 hr(11:00−15:00 HR);and the non-heat-treated control was at 30±2℃(day/night)at the same period of time for 10 d.The size of the flower buds containing meiotic pollen mother cells was determined based on the histology of DAPI stained cross section of anthers.Flower buds were embedded in optimal cutting temperature solutions(OCT)and then cut into sections of 20μm thickness.Sections containing meiotic pollen mother cells were collected using laser capture microdissection(LCM).A protein extraction procedure was optimized for the LCM collected pollen samples which yielded 25−30μg protein from 150,000−200,000 pollen cells.The heatinduced proteomes of meiotic pollen mother cells were quantified using tandem mass tag(TMT)quantitative proteomics analysis.Among the 6,343 quantified proteins,254 differentially expressed proteins(DEPs)showed significant differences in abundance level from heat treated to non-heat-treated control conditions.The heat-up-regulated-DEPs(96 proteins)include heat shock proteins,calreticulin and exocytosis(synaptobrevin)which are involved in protein folding/refolding/targeting/removal and secretion of aggregated and damaged proteins/peptides.The heat-down-regulated-DEPs(158 proteins)were involved in pathways of ubiquitin-mediated protein degradation,antioxidant mechanism,and metabolic processes of carbohydrates and lipids.Proteins affecting apoptotic programmed cell death and pollen mother cell meiotic activity were significantly changed under HS.The identified proteins and the affected biological processes could represent the major heat tolerance mechanisms during early developmental stages of male gametophyte when exposed to daily periods of above 40°C HS condition.