Assessment of the Molecular Responses of an Ancient Angiosperm against Atypical Insect Oviposition: The Case of Hass Avocados and the Tephritid Fly Anastrepha ludens

Plant Defense Responses to Insect Herbivores Through Molecular Signaling, Secondary Metabolites, and Associated Epigenetic Regulation

Over millions of years of interactions, plants have developed complex defense mechanisms to counteract diverse insect herbivory strategies. These defenses encompass morphological, biochemical, and molecular adaptations that mitigate the impacts of herbivore attacks. Physical barriers, such as spines, trichomes, and cuticle layers, deter herbivores, while biochemical defenses include the production of secondary metabolites and volatile organic compounds (VOCs). The initial step in the plant's defense involves sensing mechanical damage and chemical cues, including herbivore oral secretions and herbivore-induced VOCs. This triggers changes in plasma membrane potential driven by ion fluxes across plant cell membranes, activating complex signal transduction pathways. Key hormonal mediators, such as jasmonic acid, salicylic acid, and ethylene, orchestrate downstream defense responses, including VOC release and secondary metabolites biosynthesis. This review provides a comprehensive analysis of plant responses to herbivory, emphasizing early and late defense mechanisms, encompassing physical barriers, signal transduction cascades, secondary metabolites synthesis, phytohormone signaling, and epigenetic regulation.

Citrus Fruits Produce Direct Defense Responses against Oviposition by Bactrocera minax (Diptera: Tephritidae)

Plants perceive and orchestrate defense responses when herbivorous insects are ovipositing. Fruits, as a crucial reproductive organ in plants, have rarely been researched on the responses to insect eggs. Here, we found that oviposition by the specialist insect Bactrocera minax in navel oranges activated the lignin synthesis pathway and cell division, causing mechanical pressure that crushed the eggs. Transcriptome and metabolome analyses revealed an enrichment of oviposition-induced genes and metabolites within the lignin synthesis pathway, which was confirmed by histochemical staining. Furthermore, hydrogen peroxide (H2O2) accumulation was observed at the oviposition sites. Plant defense-related hormones jasmonic acid (JA) and salicylic acid (SA) exhibited rapid induction after oviposition, while indole-3-acetic acid (IAA) activation occurred in the later stages of oviposition. Additionally, secondary metabolites induced by prior egg deposition were found to influence larval performance. Our studies provide molecular evidence that host fruits have evolved defense mechanisms against insect eggs and pave the way for future development of insect-resistant citrus varieties.

Genome-Wide Transcriptional Response of Avocado to Fusarium sp. Infection

The avocado crop is relevant for its economic importance and because of its unique evolutionary history. However, there is a lack of information regarding the molecular processes during the defense response against fungal pathogens. Therefore, using a genome-wide approach in this work, we investigated the transcriptional response of the Mexican horticultural race of avocado (Persea americana var. drymifolia), including miRNAs profile and their possible targets. For that, we established an avocado-Fusarium hydroponic pathosystem and studied the response for 21 days. To guarantee robustness in the analysis, first, we improved the avocado genome assembly available for this variety, resulting in 822.49 Mbp in length with 36,200 gene models. Then, using an RNA-seq approach, we identified 13,778 genes differentially expressed in response to the Fusarium infection. According to their expression profile across time, these genes can be clustered into six groups, each associated with specific biological processes. Regarding non-coding RNAs, 8 of the 57 mature miRNAs identified in the avocado genome are responsive to infection caused by Fusarium, and the analysis revealed a total of 569 target genes whose transcript could be post-transcriptionally regulated. This study represents the first research in avocados to comprehensively explore the role of miRNAs in orchestrating defense responses against Fusarium spp. Also, this work provides valuable data about the genes involved in the intricate response of the avocado during fungal infection.

Reproductive behavior of fruit flies: courtship, mating, and oviposition

Many species of the Tephritidae family are invasive and cause huge damage to agriculture and horticulture, owing to their reproductive characteristics. In this review, we have summarized the existing studies on the reproductive behavior of Tephritidae, particularly those regarding the genes and external factors that are associated with courtship, mating, and oviposition. Furthermore, we outline the issues that still need to be addressed in fruit fly reproduction research. The review highlights the implications for understanding the reproductive behavior of fruit flies and discusses methods for their integrated management and biological control. © 2023 Society of Chemical Industry.

Recent Advances in Plant-Insect Interactions

Plant-insect interaction is a fast-developing research field that continues to increase the interest of numerous scientists, many of whom come from heterogeneous backgrounds [...].