Inoculation of Pochonia chlamydosporia triggers a defense response in tomato roots, affecting parasitism by Meloidogyne javanica.

Pochonia chlamydosporia is a soil-dwelling fungus and biological control agent of nematodes, active ingredient in commercial bionematicides. The fungus is also endophytically associated with the roots of several plant species, promoting their growth and inducing systemic resistance. In this study, different pathways and tomato defense metabolites were studied to identify mechanisms induced by P. chlamydosporia that contribute to the control of Meloidogyne javanica, at early and late developmental stages. Some defense responses activated by the fungus appeared related to the nematode life cycle. Among the evaluated biochemical analysis, root colonization of P. chlamydosporia showed an increase in the concentration of phenolic compounds, such as chlorogenic acid. In addition, the expression of some host plant genes was also modified. The interaction of the fungus with roots parasitized by M. javanica resulted in the highest expression of Phenylalanine Ammonia-Lyase (PAL), Chalcone synthase (LECHS 2), and Protease Inhibitor (PI1) genes at 24 days post-inoculation. At the second sampling time (44 days), there was an increase in the expression of the Respiratory Burst Oxidase Homolog (RBOH) gene. Fungus reduced the expression of the ACC-oxidase and Pathogenesis-Related Proteins 1 (PR-1) genes in roots. Moreover, P. chlamydosporia inoculation changed metabolites and phytohormone profiles of the gall formed by M. javanica. Plant defense response appeared to involve the jasmonic acid and phytosphingosine cascades. With this analysis, it was possible to propose new molecular mechanisms induced by the fungus that contribute to the control of M. javanica.

Remodeling of the cell wall as a drought-tolerance mechanism of a soybean genotype revealed by global gene expression analysis.

Drought stress is major abiotic stress that affects soybean production. Therefore, it is widely desirable that soybean becomes more tolerant to stress. To provide insights into regulatory mechanisms of the stress response, we compared the global gene expression profiles from leaves of two soybean genotypes that display different responses to water-deficit (BR 16 and Embrapa 48, drought-sensitive and drought-tolerant, respectively). After the RNA-seq analysis, a total of 5335 down-regulated and 3170 up-regulated genes were identified in the BR16. On the other hand, the number of genes differentially expressed was markedly lower in the Embrapa 48, 355 up-regulated and 471 down-regulated genes. However, induction and expression of protein kinases and transcription factors indicated signaling cascades involved in the drought tolerance. Overall, the results suggest that the metabolism of pectin is differently modulated in response to drought stress and may play a role in the soybean defense mechanism against drought. This occurs via an increase of the cell wall plasticity and crosslink, which contributed to a higher hydraulic conductance (K f) and relative water content (RWC%). The drought-tolerance mechanism of the Embrapa 48 genotype involves remodeling of the cell wall and increase of the hydraulic conductance to the maintenance of cell turgor and metabolic processes, resulting in the highest leaf RWC, photosynthetic rate (A), transpiration (E) and carboxylation (A/C i). Thus, we concluded that the cell wall adjustment under drought is important for a more efficient water use which promoted a more active photosynthetic metabolism, maintaining higher plant growth under drought stress. Supplementary Information: The online version contains supplementary material available at 10.1007/s42994-021-00043-4.