Summary
The beneficial features of Bacillus thuringiensis (Bt) are not limited to its role as an insecticide; it is also able to promote plant growth interacting with plants and other plant ...growth‐promoting rhizobacterium (PGPR). The PGPR Bt strain RZ2MS9 is a multi‐trait maize growth promoter. We obtained a stable mutant of RZ2MS9 labelled with green fluorescent protein (RZ2MS9‐GFP). We demonstrated that the Bt RZ2MS9‐GFP successfully colonizes maize's roots and leaves endophytically. We evaluated whether RZ2MS9 has an additive effect on plant growth promotion when co‐inoculated with Azospirillum brasilense Ab‐V5. The two strains combined enhanced maize's roots and shoots dry weight around 50% and 80%, respectively, when compared to the non‐inoculated control. However, non‐differences were observed comparing RZ2MS9 alone and when co‐inoculated with Ab‐V5, In addition, we used co‐inoculation experiments in glass chambers to analyse the plant's volatile organic compounds (VOCs) production during the maize‐RZ2MS9 and maize‐RZ2MS9‐Ab‐V5 interaction. We found that the single and co‐inoculation altered maize's VOCs emission profile, with an increase in the production of indoles in the co‐inoculation. Collectively, these results increase our knowledge about the interaction between the Bt and maize, and provide a new possibility of combined application with the commercial inoculant A. brasilense Ab‐V5.
ABSTRACT Common bean (Phaseolus vulgaris L.) is a leguminous species of great economic and nutritional importance worldwide, and thus the development of management strategies to promote plant growth ...and increase grain yield of legumes is of great interest to farmers. The growth-promoting effects of the symbiosis of endophytic microorganisms in plants have been exploited in several crops. This study investigated the effects of Induratia sp. endophytic fungi on the growth and grain yield of seed-inoculated common bean plants. The experiments were conducted in a greenhouse during two growing seasons using a randomized complete block design with three replicates. Growth and yield-related parameters such as plant height, root length, leaf index, number of days for flowering, number of pods per plant, number of grains per pod, mass of 100 grains, and grain yield were evaluated. The grain yield of plants inoculated with Induratia coffeana strains CML 4018 and CML 4020 and Induratia sp. strain CML 4015 increased by 52.5%, 48.9%, and 56.4% compared to the non-inoculated control, respectively. Seed inoculation of common bean plants with endophytic fungi species of the genus Induratia showed a beneficial interaction as indicated by the recorded increase in grain yield. The present pioneering study could provide the means for developing crop management strategies for enhancing common bean crop productivity.
RESUMO O feijoeiro comum (Phaseolus vulgaris L.) é uma leguminosa de grande importância econômica e nutricional em todo o mundo; portanto, o desenvolvimento de estratégias de manejo para promover o crescimento das plantas e aumentar a produtividade de grãos é de grande interesse para os agricultores. Os efeitos da promoção de crescimento por simbiose de microrganismos endofíticos com plantas têm sido explorados em várias culturas. Este estudo investigou os efeitos sobre o crescimento e a produtividade de grãos em feijoeiro por meio de fungos endofíticos Induratia inoculados em sementes. Os experimentos foram conduzidos em casa de vegetação no delineamento de blocos completos casualizados com três repetições. Foram avaliados a altura de planta, comprimento de raiz, índice foliar, número de dias para o florescimento, número de vagens por planta, número de grãos por vagem, massa de 100 grãos e produtividade de grãos. A produtividade das plantas inoculadas com Induratia coffeana (CML 4018, CML 4020) e Induratia sp. (CML 4015) aumentou 52,5%, 48,9% e 56,4%, respectivamente, em comparação com os controles. A inoculação de sementes de feijão com espécies de fungos endofíticos do gênero Induratia apresentou interação benéfica, aumentando a produtividade de grãos. Este estudo pioneiro é importante para o desenvolvimento de estratégias de manejo visando o aumento da produtividade do feijoeiro.
The bacterial biosynthesis of indole-3-acetic acid (IAA) is often related to the beneficial effects of plant growth-promoting rhizobacteria (PGPR) on plant development. In PGPR belonging to the ...Bacillus genus, the synthesis of IAA may occur through different metabolic pathways that are still poorly understood. B. thuringiensis (Bt) is well known for its insecticidal properties; however, its beneficial features are not limited to pest control. Our group has been studed the beneficial effects of Bt strain RZ2MS9 as growth promoter in a range of plant crops, including soybean, tomato, and maize. We recently demonstrated that bacterial IAA biosynthesis plays an important role in the ability of RZ2MS9 to benefit plant development. However, the molecular involved mechanisms in the IAA biosynthesis by this bacterium in the beneficial interaction with plants remain unclear. Here, we investigated the genetic basis of IAA biosynthesis by RZ2MS9. We knocked out the ipdC gene, involved in IAA biosynthesis via the tryptophan-dependent IPyA pathway, using the CRISPR-Cas9 system. Our results showed that, by disrupting the IPyA pathway, the amount of IAA synthesized by the mutant RZ2MS9 (ΔipdC) in the presence of tryptophan drops 57%. The gene knockout did not affect the bacterial growth, but it did affect its ability to colonize maize. Moreover, deactivating the ipdC gene in RZ2MS9 significantly reduces its ability to promote maize growth. ΔipdC performed worse than RZ2MS9 in almost all evaluated plant parameters, including total root length, projected root area, lateral roots, aerial part dry matter, and germination speed index. Therefore, we demonstrated that tryptophan-dependent IAA biosynthesis via the IPyA pathway by RZ2MS9 is strongly influenced by the ipdC gene. Furthermore, IAA biosynthesis by RZ2MS9 is a major mechanism used by this PGPR to promote maize growth.
Austropuccinia psidii is a biotrophic fungus that causes myrtle rust. First described in Brazil, it has since spread to become a globally important pathogen that infects more than 480 myrtaceous ...species. One of the most important commercial crops affected by A. psidii is eucalypt, a widely grown forestry tree. The A. psidii–Eucalyptus spp. interaction is poorly understood, but pathogenesis is likely driven by pathogen-secreted effector molecules. Here, we identified and characterized a total of 255 virulence effector candidates using a genome assembly of A. psidii strain MF-1, which was recovered from Eucalyptus grandis in Brazil. We show that the expression of seven effector candidate genes is modulated by cell wax from leaves sourced from resistant and susceptible hosts. Two effector candidates with different subcellular localization predictions, and with specific gene expression profiles, were transiently expressed with GFP-fusions in Nicotiana benthamiana leaves. Interestingly, we observed the accumulation of an effector candidate, Ap28303, which was upregulated under cell wax from rust susceptible E. grandis and described as a peptidase inhibitor I9 domain-containing protein in the nucleus. This was in accordance with in silico analyses. Few studies have characterized nuclear effectors. Our findings open new perspectives on the study of A. psidii–Eucalyptus interactions by providing a potential entry point to understand how the pathogen manipulates its hosts in modulating physiology, structure, or function with effector proteins.
Austropuccinia psidii is a biotrophic fungus that causes myrtle rust. First described in Brazil, it has since spread to become a globally important pathogen that infects more than 480 myrtaceous ...species. One of the most important commercial crops affected by A. psidii is eucalypt, a widely grown forestry tree. The A. psidii–Eucalyptus spp. interaction is poorly understood, but pathogenesis is likely driven by pathogen-secreted effector molecules. Here, we identified and characterized a total of 255 virulence effector candidates using a genome assembly of A. psidii strain MF-1, which was recovered from Eucalyptus grandis in Brazil. We show that the expression of seven effector candidate genes is modulated by cell wax from leaves sourced from resistant and susceptible hosts. Two effector candidates with different subcellular localization predictions, and with specific gene expression profiles, were transiently expressed with GFP-fusions in Nicotiana benthamiana leaves. Interestingly, we observed the accumulation of an effector candidate, Ap28303, which was upregulated under cell wax from rust susceptible E. grandis and described as a peptidase inhibitor I9 domain-containing protein in the nucleus. This was in accordance with in silico analyses. Few studies have characterized nuclear effectors. Our findings open new perspectives on the study of A. psidii–Eucalyptus interactions by providing a potential entry point to understand how the pathogen manipulates its hosts in modulating physiology, structure, or function with effector proteins.
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