Gall
Galls (from the Latin galla, 'oak-apple') or cecidia (from the Greek kēkidion, anything gushing out) are a kind of swelling growth on the external tissues of plants.
Factors influencing gall morphology include plant species, tissue type, gall-inducing agent, and environmental conditions.
[8] Plant response involves the establishment of metaplasied cells and localized metabolic changes to repair the wound and neutralize stress.
[2] Insects such as wasps, moths, and flies, possessing chewing mouthparts during their adult or larval stages, typically inhabit completely enclosed galls.
Upon reaching maturity, the adult exits either by chewing its way out or utilizing an opening created by the larval stage.
[3][18] Insects induce the formation of galls on plants from which they receive various services, such as a source of nutrition and a place to lay eggs, develop, and be provided protection from the environment and enemies.
[23] Additionally, gall frequency varies based on factors such as weather, plant susceptibility, and pest populations.
Gall tissues are nutritive and present high concentrations of lipids, proteins, nitrogen, and other nutrients.
The presence of stress and insect secretions stimulates the synthesis of growth-promoting substances, possibly involving a combination of different growth promoters like auxins and kinins.
The 'zigzag' model introduced by Jones & Dangl (2006)[26] demonstrates the molecular interactions underlying gall induction.
This model, refined over time and subject to ongoing enhancements, illustrates the intricate dynamics between antagonistic molecular players.
Pattern-triggered immunity (PTI), constitutes the initial defense layer of plant cells, activated upon detection of "danger signals."
PRRs, classified as receptor-like kinases (RLKs), mediate intercellular communication by bridging external stimuli with intracellular defense mechanisms.
Effectoromics, involving high-throughput expression screens, aids in identifying effector candidates crucial for colonization.
Conversely, Effector-Triggered Immunity (ETI) responsible for plant's counterattack, leveraging effectors as "danger signals" to render the parasite avirulent.
During ETI, nucleotide-binding domain leucine-rich repeat (NLR)-containing receptors detect perturbations induced by effectors, leading to downstream signaling events that promote defense responses.
However, parasites can counteract ETI by modifying ETS, undermining the efficacy of resistance genes deployed in agriculture.
The evolutionary arms race between plants and parasites, underscored by the expansion of gene families involved in biotic interactions, shapes their genomic landscape, influencing their adaptive strategies and diversification.
[2] Certain bacteria, like Rhodococcus fascians, induce the formation of leafy galls on plants, affecting their growth.
These galls act as permanent sinks, diverting nutrients away from other parts of the plant and causing growth suppression elsewhere.
While parasitic gall-inducers are typically harmful to plants, researchers are exploring ways to harness their growth-promoting abilities for agricultural benefit.
The defense-related genes are found to be suppressed in inner gall tissues as a strategy to accommodate the feeding activity of the parasite.
To form galls, the insects must take advantage of the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics.
The fungus Ustilago esculenta associated with Zizania latifolia, a wild rice, produces an edible gall highly valued as a food source in the Zhejiang and Jiangsu provinces of China.
[41] More complex interactions are possible; the parasitic plant Cassytha filiformis sometimes preferentially feeds on galls induced by the cynipid wasp Belonocnema treatae.
[42] Insects induce the formation of galls on plants from which they receive various services, such as a source of nutrition and a place to lay eggs, develop, and be provided protection from the environment and enemies.
[23] Additionally, gall frequency varies based on factors such as weather, plant susceptibility, and pest populations.
Gall tissues are nutritive and present high concentrations of lipids, proteins, nitrogen, and other nutrients.
