Transcriptomic and Metabolomic Analysis of Wheat Kernels in Response to the Feeding of Orange Wheat Blossom Midges (Sitodiplosis mosellana) in the Field

Salinity stress alters plant-mediated interactions between above- and below-ground herbivores

Below-ground herbivory impacts plant development and often induces systemic responses in plants that affect the performance and feeding behavior of above-ground herbivores. Meanwhile, pest-damaged root tissue can enhance a plant's susceptibility to abiotic stress such as salinity. Yet, the extent to which herbivore-induced plant defenses are modulated by such abiotic stress has rarely been studied. In this study, we examine whether root feeding by larvae of the turnip moth, Agrotis segetum (Lepidoptera: Noctuidae) affects the performance of the above-ground, sap-feeding aphid Aphis gossypii (Hemiptera: Aphididae) on cotton, and assess whether those interactions are modulated by salinity stress. In the absence of salinity stress, A. segetum root feeding does not affect A. gossypii development. On the other hand, under intense salinity stress (i.e., 600 mM NaCl), A. segetum root feeding decreases aphid development time by 16.1 % and enhances fecundity by 72.0 %. Transcriptome, metabolome and bioassay trials showed that root feeding and salinity stress jointly trigger the biosynthesis of amino acids in cotton leaves. Specifically, increased titers of valine in leaf tissue relate to an enhanced performance of A. gossypii. Taken together, salinity stress alters the interaction between above- and below-ground feeders by changing amino acid accumulation. Our findings advance our understanding of how plants cope with concurrent biotic and abiotic stressors, and may help tailor plant protection strategies to varying production contexts.

Enhancing cowpea wilt resistance: insights from gene coexpression network analysis with exogenous melatonin treatment

BACKGROUND

Cowpea wilt is a harmful disease caused by Fusarium oxysporum, leading to substantial losses in cowpea production. Melatonin reportedly regulates plant immunity to pathogens; however the specific regulatory mechanism underlying the protective effect of melatonin pretreated of cowpea against Fusarium oxysporum remains known. Accordingly, the study sought to evaluate changes in the physiological and biochemical indices of cowpea following melatonin treated to facilitate Fusarium oxysporum resistance and elucidate the associated molecular mechanism using a weighted gene coexpression network.

RESULTS

Treatment with 100 µM melatonin was effective in increasing cowpea resistance to Fusarium oxysporum. Glutathione peroxidase (GSH-PX), catalase (CAT), and salicylic acid (SA) levels were significantly upregulated, and hydrogen peroxide (H2O2) levels were significantly downregulated in melatonin treated samples in roots. Weighted gene coexpression network analysis of melatonin- and Fusarium oxysporum-treated samples identified six expression modules comprising 2266 genes; the number of genes per module ranged from 9 to 895. In particular, 17 redox genes and 32 transcription factors within the blue module formed a complex interconnected expression network. KEGG analysis revealed that the associated pathways were enriched in secondary metabolism, peroxisomes, phenylalanine metabolism, flavonoids, and flavonol biosynthesis. More specifically, genes involved in lignin synthesis, catalase, superoxide dismutase, and peroxidase were upregulated. Additionally, exogenous melatonin induced activation of transcription factors, such as WRKY and MYB.

CONCLUSIONS

The study elucidated changes in the expression of genes associated with the response of cowpea to Fusarium oxysporum under melatonin treated. Specifically, multiple defence mechanisms were initiated to improve cowpea resistance to Fusarium oxysporum.

Combining transcriptome and metabolome analysis to understand the response of sorghum to Melanaphis sacchari

BACKGROUND

The sorghum aphid Melanaphis sacchari (Zehntner) (Homoptera: Aphididae) is an important insect in the late growth phase of sorghum (Sorghum bicolor L.). However, the mechanisms of sorghum response to aphid infestation are unclear.

RESULTS

In this paper, the mechanisms of aphid resistance in different types of sorghum varieties were revealed by studying the epidermal cell structure and performing a transcriptome and metabolome association analysis of aphid-resistant and aphid-susceptible varieties. The epidermal cell results showed that the resistance of sorghum to aphids was positively correlated with epidermal cell regularity and negatively correlated with the intercellular space and leaf thickness. Transcriptome and metabolomic analyses showed that differentially expressed genes in the resistant variety HN16 and susceptible variety BTX623 were mainly enriched in the flavonoid biosynthesis pathway and differentially expressed metabolites were mainly related to isoflavonoid biosynthesis and flavonoid biosynthesis. The q-PCR results of key genes were consistent with the transcriptome expression results. Meanwhile, the metabolome test results showed that after aphidinfestation, naringenin and genistein were significantly upregulated in the aphid-resistant variety HN16 and aphid-susceptible variety BTX623 while luteolin was only significantly upregulated in BTX623. These results show that naringenin, genistein, and luteolin play important roles in plant resistance to aphid infestation. The results of exogenous spraying tests showed that a 1‰ concentration of naringenin and genistein is optimal for improving sorghum resistance to aphid feeding.

CONCLUSIONS

In summary, the physical properties of the sorghum leaf structure related to aphid resistance were studied to provide a reference for the breeding of aphid-resistant varieties. The flavonoid biosynthesis pathway plays an important role in the response of sorghum aphids and represents an important basis for the biological control of these pests. The results of the spraying experiment provide insights for developing anti-aphid substances in the future.

Characterization of three glutathione S-transferases potentially associated with adaptation of the wheat blossom midge Sitodiplosis mosellana to host plant defense

BACKGROUND

Insect glutathione S-transferases (GSTs), a multifunctional protein family, play a crucial role in detoxification of plant defensive compounds. However, they have been rarely investigated in Sitodiplosis mosellana, a destructive pest of wheat worldwide. In this study, we characterized for the first time a delta (SmGSTd1) and two epsilon GST genes (SmGSTe1 and SmGSTe2) and analyzed their expression patterns and functions associated with adaptation to host plant defense in this species.

RESULTS

Expression of these SmGST genes greatly increased in S. mosellana larvae feeding on resistant wheat varieties Kenong1006, Shanmai139 and Jinmai47 which contain higher tannin and ferulic acid, the major defensive compounds of wheat against this pest, compared with those feeding on susceptible varieties Xinong822, Xinong88 and Xiaoyan22. Their expression was also tissue-specific, most predominant in larval midgut. Recombinant SmGSTs expressed in Escherichia coli could catalyze the conjugation of 1-chloro-2,4-dinitrobenzene, with activity peak at pH around 7.0 and temperature between 30 and 40 °C. Notably, they could metabolize tannin and ferulic acid, with the strongest metabolic ability by SmGSTe2 against two compounds, followed by SmGSTd1 on tannin, and SmGSTe1 on ferulic acid.

CONCLUSION

The results suggest that these SmGSTs are important in metabolizing wheat defensive chemicals during feeding, which may be related to host plant adaptation of S. mosellana. Our study has provided information for future investigation and development of strategies such as host-induced gene silencing of insect-detoxifying genes for managing pest adaptation. © 2023 Society of Chemical Industry.

Combined analysis of metabolome and transcriptome of wheat kernels reveals constitutive defense mechanism against maize weevils

Sitophilus zeamais (maize weevil) is one of the most destructive pests that seriously affects the quantity and quality of wheat (Triticum aestivum L.). However, little is known about the constitutive defense mechanism of wheat kernels against maize weevils. In this study, we obtained a highly resistant variety RIL-116 and a highly susceptible variety after two years of screening. The morphological observations and germination rates of wheat kernels after feeding ad libitum showed that the degree of infection in RIL-116 was far less than that in RIL-72. The combined analysis of metabolome and transcriptome of RIL-116 and RIL-72 wheat kernels revealed differentially accumulated metabolites were mainly enriched in flavonoids biosynthesis-related pathway, followed by glyoxylate and dicarboxylate metabolism, and benzoxazinoid biosynthesis. Several flavonoids metabolites were significantly up-accumulated in resistant variety RIL-116. In addition, the expression of structural genes and transcription factors (TFs) related to flavonoids biosynthesis were up-regulated to varying degrees in RIL-116 than RIL-72. Taken together, these results indicated that the biosynthesis and accumulation of flavonoids contributes the most to wheat kernels defense against maize weevils. This study not only provides insights into the constitutive defense mechanism of wheat kernels against maize weevils, but may also play an important role in the breeding of resistant varieties.

Flavonoid Synthesis-Related Genes Determine the Color of Flower Petals in Brassica napus L

The color of rapeseed (Brassica napus L.) petal is usually yellow but can be milky-white to orange or pink. Thus, the petal color is a popular target in rapeseed breeding programs. In his study, metabolites and RNA were extracted from the yellow (Y), yellow/purple (YP), light purple (LP), and purple (P) rapeseed petals. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), RNA-Seq, and quantitative real-time (qRT-PCR) analyses were performed to analyze the expression correlation of differential metabolites and differential genes. A total of 223 metabolites were identified in the petals of the three purple and yellow rapeseed varieties by UPLC-MS/MS. A total of 20511 differentially expressed genes (DEGs) between P, LP, YP, versus Y plant petals were detected. This study focused on the co-regulation of 4898 differential genes in the three comparison groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotation and quantitative RT-PCR analysis showed that the expression of BnaA10g23330D (BnF3H) affects the synthesis of downstream peonidin and delphinidin and is a key gene regulating the purple color of petals in B. napus. L. The gene may play a key role in regulating rapeseed flower color; however, further studies are needed to verify this. These results deepen our understanding of the molecular mechanisms underlying petal color and provide the theoretical and practical basis for flower breeding targeting petal color.

Wheat Long Noncoding RNAs from Organelle and Nuclear Genomes Carry Conserved microRNA Precursors Which May Together Comprise Intricate Networks in Insect Responses

Long noncoding RNAs (lncRNAs) are a diverse class of noncoding RNAs that are typically longer than 200 nucleotides but lack coding potentials. Advances in deep sequencing technologies enabled a better exploration of this type of noncoding transcripts. The poor sequence conservation, however, complicates the identification and annotation of lncRNAs at a large scale. Wheat is among the leading food staples worldwide whose production is threatened by both biotic and abiotic stressors. Here, we identified putative lncRNAs from durum wheat varieties that differ in stem solidness, a major source of defense against wheat stem sawfly, a devastating insect pest. We also analyzed and annotated lncRNAs from two bread wheat varieties, resistant and susceptible to another destructive pest, orange wheat blossom midge, with and without infestation. Several putative lncRNAs contained potential precursor sequences and/or target regions for microRNAs, another type of regulatory noncoding RNAs, which may indicate functional networks. Interestingly, in contrast to lncRNAs themselves, microRNAs with potential precursors within the lncRNA sequences appeared to be highly conserved at the sequence and family levels. We also observed a few putative lncRNAs that have perfect to near-perfect matches to organellar genomes, supporting the recent observations that organellar genomes may contribute to the noncoding transcript pool of the cell.

Plant Volatiles Mediate Host Selection of Sitodiplosis mosellana (Diptera: Cecidomyiidae) among Wheat Varieties

Sitodiplosis mosellana is a major wheat pest that oviposits on spikes, and resistant wheat varieties have been released. However, wheat spike volatiles mediating S. mosellana host selection or resistance are largely unknown. In this study, we found that the highly susceptible wheat varieties Xinong 822, Xinong 88, and Xiaoyan 22 were preferred for S. mosellana oviposition, and their spike volatiles were more attractive to females compared to the resistant varieties Kenong 1006, Shanmai 139, and Jinmai 47. Importantly, we found five odor components evoking obvious concentration-dependent electroantennogram (EAG) and behavioral response. Notably, 3-hexanol, cis-3-hexenylacetate, and hexyl acetate strongly attracted females, whereas ocimene, a dominant component of three resistant varieties, and α-farnesene, absent in Xinong 88, repelled females. Significant attraction was also observed in a synthetic blend mimicking Xinong 822 volatiles. These results suggest that these wheat volatiles are involved in host selection of S. mosellana and provide a basis for development of semichemical-based pest management.