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Galls are neoformed structures induced by specific animals, fungi, bacteria, virus or some parasitic plants on their host plant organs. Developmental processes are well known in Agrobacterium tumefasciens galls, but the animal-induced galls have a striking anatomical diversity, concerning several patterns, which were reunited herein. Anatomical traits observed in animal-induced galls involve manipulation of plant morphogenesis in convergent ways. Nematode, mite and insect galls usually contain homogeneous storage parenchyma and develop due to hyperplasia and cell hypertrophy. The development of typical nutritive tissues, giant cells, or hypertrophied vascular bundles may occur. Some other anatomical features may be usually restricted to galls induced by specific taxa, but they may eventually be related to the developmental potentialities of the host plants. The combination of distinct morphogenetic peculiarities in each gall system culminates in extant gall structural diversity. Convergent anatomical traits are observed according to the feeding mode of the gall inducers, representing potentiation or inhibition of similar events of host plant morphogenesis and cell redifferentiation, independent of gall-inducing taxa.

Abstract Fabaceae stands out as the primary plant family hosting galls in Brazil. Based on data from Brazilian literature, we compiled and listed the structural and histochemical traits related to the development of 26 gall morphotypes induced in 13 Fabaceae species. The inherent plasticity of this plant family enables multiple functionalities and facilitates its adaptation to a wide range of environments. We hypothesize that the interaction between distinct host Fabaceae traits and their multiple functionalities offers galling herbivores a wide variety of structural and chemical resources. A current literature survey reveals that epidermal alterations, parenchyma homogenization, and cell wall lignification are the primary gall traits that confer a physical, mechanical, and biochemical combination, enabling the success of the gall inducer life cycle. The multiple functionalities of these traits may enhance the adaptability of Fabaceae galls in different environments. Furthermore, the range of possibilities offered by each structural peculiarity, in combination with chemical traits and the regulation of key enzymes in carbohydrate metabolism, indicates the existence of sophisticated physiological and biochemical relationships. Our data also reveal peculiarities of species within the subfamily Caesalpinioideae, which act as superhosts of galling herbivores and may serve as elegant models for future studies on galls in the Neotropical region. We provide insights into three Fabaceae host plant-gall inducer systems and encourage researchers to continue mapping their ontogenetic steps toward elucidating changes in standard developmental plant programs, while advancing our understanding of gall diversity. Resumo Fabaceae se destaca como a principal família de plantas hospedeiras de galhas no Brasil. Com base em dados da literatura brasileira, compilamos e listamos as características estruturais e histoquímicas relacionadas ao desenvolvimento de 26 morfotipos de galhas induzidos em 13 espécies de Fabaceae. A plasticidade inerente as plantas desta família garante múltiplas funcionalidades e facilita sua adaptabilidade a diversos ambientes. Nossa hipótese é que a interação entre características distintas das Fabaceae hospedeiras e suas múltiplas funcionalidades oferece aos herbívoros galhadores uma ampla variedade de recursos estruturais e químicos. Os dados de literatura aqui reunidos indicam que as alterações epidérmicas, homogeneização do parênquima e lignificação da parede celular conferem uma combinação física, mecânica e bioquímica que garante o sucesso do ciclo de vida do galhador. As múltiplas funcionalidades destas mesmas características podem aumentar a adaptabilidade das galhas em Fabaceae a diferentes ambientes. Além disso, a gama de possibilidades oferecidas por cada atributo estrutural, em combinação com características químicas e a regulação de enzimas-chave no metabolismo de carboidratos, indica relações fisiológicas e bioquímicas sofisticadas. Nossos dados também revelam que as peculiaridades das espécies da subfamília Caesalpinioideae, que atuam como superhospedeiras de herbívoros galhadores, podem ser modelos elegantes para estudos futuros em galhas na região Neotropical. Fornecemos informações sobre três sistemas planta hospedeira-organismo indutor de galhas da família Fabaceae, com o objetivo de incentivar os pesquisadores a continuar mapeando as etapas ontogenéticas que levam a mudanças nos programas de desenvolvimento padrão das plantas, contribuindo ainda para o avanço do conhecimento sobre a diversidade de galhas.

Galls are characteristic plant structures formed by cell size enlargement and/or cell proliferation induced by parasitic or pathogenic organisms. Insects are a major inducer of galls, and insect galls can occur on plant leaves, stems, floral buds, flowers, fruits, or roots. Many of these exhibit unique shapes, providing shelter and nutrients to insects. To form unique gall structures, gall-inducing insects are believed to secrete certain effector molecules and hijack host developmental programs. However, the molecular mechanisms of insect gall induction and development remain largely unknown due to the difficulties associated with the study of non-model plants in the wild. Recent advances in next-generation sequencing have allowed us to determine the biological processes in non-model organisms, including gall-inducing insects and their host plants. In this review, we first summarize the adaptive significance of galls for insects and plants. Thereafter, we summarize recent progress regarding the molecular aspects of insect gall formation.

The reduction of the use chemical pesticides in agriculture is gaining importance as an objective of decision-makers in both politics and economics. Consequently, the development of technically efficient and economically affordable alternatives as, e.g., biological control agents or practices is highly solicited. Crown gall disease of dicotyledonous plants is caused by ubiquitous soil borne pathogenic bacteria of the Agrobacterium tumefaciens species complex, that comprises the species Agrobacterium fabrum and represents a globally relevant plant protection problem. Within the framework of a screening program for bacterial Agrobacterium antagonists a total of 14 strains were isolated from Tunisian soil samples and assayed for antagonistic activity against pathogenic agrobacteria. One particularly promising isolate, termed strain MBY2, was studied more in depth. Using a Multilocus Sequence Analysis (MLSA) approach, the isolate was assigned to the taxonomic species Bacillus velezensis . Strain MBY2 was shown to display antagonistic effects against the pathogenic A . fabrum strain C58 in vitro and to significantly decrease pathogen populations under sterile and non-sterile soil conditions as well as in the rhizosphere of maize and, to a lower extent, tomato plants. Moreover, the ability of B . velezensis MBY2 to reduce C58-induced gall development has been demonstrated in vivo on stems of tomato and almond plants. The present study describes B . velezensis MBY2 as a newly discovered strain holding potential as a biological agent for crown gall disease management.

Grapevine crown gall (GCG), caused by tumor-inducing strains of Allorhizobium vitis (= Rhizobium vitis), is a threat to grapevines around the world. Previously, nonpathogenic A. vitis strain ARK-1 emerged as a promising biological control agent, demonstrating remarkable efficacy in root soaking procedures before planting. This study aims to evaluate the treatment effects when applying soil injection procedures post-planting, both in greenhouse and field experiments. The results of the treatment effects obtained from 21 experiments over 9 years (2009 to 2017) were analyzed and evaluated by a general linear mixed model (GLMM) and a network meta-analysis (NMA). The GLMM results revealed a significant association between the factors \"soil injection\" and \"root soaking\" with biological control activity. Subsequently, the NMA results showed that the estimated relative ratio (RR) following root soaking and soil injection treatments with ARK-1 was 0.16 and 0.30, respectively. In summary, while the control efficacy of root soaking with ARK-1 exceeded that of soil injection, the latter method also proved effective in managing GCG. Therefore, soil injection is recommended as a viable approach for GCG control.

Abstract We surveyed woody plants, including oaks and chestnuts (Quercus L. and Castanea Mill.), and recorded the inhabiting galls induced by oak gall wasps (Hymenoptera: Cynipidae: Cynipini) at seven Japanese semi-natural grassland sites maintained by traditional regular burning with two of the seven abandoned grassland areas. Woody plants were established in all burned and abandoned grasslands. Oak species were found at four of the seven sites. In total, 15 types of cynipid galls were recorded at all four sites where oak species were found. However, the occurrence of species was site-specific for host trees and cynipid galls. Although a few ecological studies of oak gall wasps inhabiting grassland environments, which have rapidly decreased in recent decades, have been conducted, this study suggests that semi-natural grasslands may be potential habitats for oak gall wasps and their host trees, and we provide a checklist of oak gall wasps with host oak records in semi-natural grasslands throughout Japan.

infection of wounded plant tissues causes the formation of crown gall tumors. Upon infection, genes encoded on the tumor inducing plasmid are integrated in the plant genome to induce the biosynthesis of auxin and cytokinin, leading to uncontrolled cell division. Additional sequences present on the bacterial T-DNA encode for opine biosynthesis genes, which induce the production of opines that act as a unique carbon and nitrogen source for . Crown galls therefore become a very strong sink for photosynthate. Here we found that the increased metabolic demand in crown galls causes an increase in oxygen consumption rate, which leads to a steep drop in the internal oxygen concentration. Consistent with this, plant hypoxia-responsive genes were found to be significantly upregulated in crown galls compared to uninfected stem tissue. Following this observation, we aimed at understanding whether the low-oxygen response pathway, mediated by group VII ethylene response factor (ERF-VII) transcription factors, plays a role in the development of crown galls. We found that quintuple knock-out mutants of all ERF-VII members, which are incapable of inducing the hypoxic response, show reduced crown gall symptoms. Conversely, mutant genotypes characterized by constitutively high levels of hypoxia-associated transcripts, displayed more severe crown gall symptoms. Based on these results, we concluded that uncontrolled cell proliferation of crown galls established hypoxic conditions, thereby requiring adequate anaerobic responses of the plant tissue to support tumor growth.

Main conclusionPlant responds to Agrobacterium via three-layered immunity that determines its susceptibility or resistance to Agrobacterium infection.Agrobacterium tumefaciens is a soil-borne Gram-negative bacterium that causes crown gall disease in plants. The remarkable feat of interkingdom gene transfer has been extensively utilised in plant biotechnology to transform plant as well as non-host systems. In the past two decades, the molecular mode of the pathogenesis of A. tumefaciens has been extensively studied. Agrobacterium has also been utilised as a premier model to understand the defence response of plants during plant–Agrobacterium interaction. Nonetheless, the threat of Agrobacterium-mediated crown gall disease persists and is associated with a huge loss of plant vigour in agriculture. Understanding the molecular dialogues between these two interkingdom species might provide a cure for crown gall disease. Plants respond to A. tumefaciens by mounting a three-layered immune response, which is manipulated by Agrobacterium via its virulence effector proteins. Comparative studies on plant defence proteins versus the counter-defence of Agrobacterium have shed light on plant susceptibility and tolerance. It is possible to manipulate a plant’s immune system to overcome the crown gall disease and increase its competence via A. tumefaciens-mediated transformation. This review summarises the recent advances in the molecular mode of Agrobacterium pathogenesis as well as the three-layered immune response of plants against Agrobacterium infection.

This study describes differences in species richness and composition of the assemblages of galling insects and their host plants at different spatial scales. Sampling was conducted along altitudinal gradients composed of campos rupestres and campos de altitude of two mountain complexes in southeastern Brazil: Espinhaço Range and Mantiqueira Range. The following hypotheses were tested: i) local and regional richness of host plants and galling insects are positively correlated; ii) beta diversity is the most important component of regional diversity of host plants and galling insects; and iii) Turnover is the main mechanism driving beta diversity of both host plants and galling insects. Local richness of galling insects and host plants increased with increasing regional richness of species, suggesting a pattern of unsaturated communities. The additive partition of regional richness ([gamma]) into local and beta components shows that local richnesses ([alpha]) of species of galling insects and host plants are low relative to regional richness; the beta ([beta]) component incorporates most of the regional richness. The multi-scale analysis of additive partitioning showed similar patterns for galling insects and host plants with the local component ([alpha]) incorporated a small part of regional richness. Beta diversity of galling insects and host plants were mainly the result of turnover, with little contribution from nesting. Although the species composition of galling insects and host plant species varied among sample sites, mountains and even mountain ranges, local richness remained relatively low. In this way, the addition of local habitats with different landscapes substantially affects regional richness. Each mountain contributes fundamentally to the composition of regional diversity of galling insects and host plants, and so the design of future conservation strategies should incorporate multiple scales.

Galls are products of the hyperplasia of host plant structures induced by gall-inducing organisms and have been considered as an extended phenotype of the inducers. There is little evidence regarding the effect of host plants on gall morphology. We hypothesised that the morphology and developmental pattern of galls are different because of the different location of their stimulation, even though two kinds of inducers are close relatives. We observed that horned galls and their leaflets of their host plant, Rhus chinensis required a longer rapid growth stage than fusiform galls and Rhus potaninii leaflets. The distribution of trichomes showed positional dependence. Molecular analysis showed that in the fusiform gall, the target genes that regulate the plastochron of leaflets and serration development were hardly expressed, and CUP-SHAPED COTYLEDON-2 may be a key gene that regulates the formation of the horns. In summary, horned and fusiform galls showed a developmental pattern similar to those of their host plant leaflets. We suggest that the inducing site is important in the morphology and development of galls.