Saúl Fraire-Velázquez

Abiotic and Biotic Stress Response Crosstalk in Plants

In the course of its evolution, plants have developed mechanisms to cope with and adapt to different types of abiotic and biotic stress imposed by the frequently adverse environment. The biology of a cell or cells in tissues is so complicated that with any given stimulus from the environment, multiple pathways of cellular signaling that have complex interactions or crosstalk are activated; these interactions probably evolved as mechanisms to enable the live systems to respond to stress with minimal and appropriate biological processes. The sensing of biotic and abiotic stress induces signaling cascades that activate ion channels, kinase cascades, production of reactive oxygen species (ROS), accumulation of hormones such as salicylic acid (SA), ethylene (ET), jasmonic acid (JA) and abscisic acid (ABA). These signals ultimately induce expression of specific sub-sets of defense genes that lead to the assembly of the overall defense reaction. In plants, defense response genes are transcriptionally activated by different forms of environmental stress or by pathogens. The induction of expression of defense genes in the response against certain pathogens is further dependent on temperature and humidity, suggesting the existence of a complex signaling network that allows the plant to recognize and protect itself against pathogens and environmental stress. A body of research has shown that calcium and reactive oxygen species are second messengers in the early response to abiotic and biotic stress. For example, cytosolic calcium (Ca2+) levels increase in plant cells in response to various harsh environmental conditions, including pathogen attack, osmotic stress, water stress, cold and wounding. After the increase of Ca2+ concentration in the intracellular space, several simultaneous pathways are activated by calcium-interacting proteins such as Ca2+-dependent protein kinases (CDPKs), calmodulin and calcineurin Blike proteins (CBLs), all proteins with the structural ‘EF-hand’ calcium-binding motif. It is also known that plants respond with an oxidative burst to avirulent microbial intruders or to the previously mentioned abiotic stress factors. In this response, NADPH oxidases generate O2– that is rapidly converted to H2O2. Recent evidence demonstrated that the NADPH oxidases are activated by Ca2+ signatures. ROS are generated by NADPH oxidases

Abiotic Stress in Plants and Metabolic Responses

The vast metabolic diversity observed in plants is the direct result of continuous evolutionary processes. There are more than 200,000 known plant secondary metabolites, representing a vast reservoir of diverse functions. When the environment is adverse and plant growth is affected, metabolism is profoundly involved in signaling, physiological regulation, and defense responses. At the same time, in feedback, abiotic stresses affect the biosynthesis, concentration, transport, and storage of primary and secondary metabolites. Metabolic adjustments in response to abiotic stressors involve fine adjustments in amino acid, carbohy‐ drate, and amine metabolic pathways. Proper activation of early metabolic responses helps cells restore chemical and energetic imbalances imposed by the stress and is crucial to acclimation and survival. Time-series experiments have revealed that metabolic activities respond to stress more quickly than transcriptional activities do. In order to study and map all the simultaneous metabolic responses and, more importantly, to link these responses to a specific abiotic stress, integrative and comprehensive analyses are required. Metabolomics is the systematic approach through which qualitative and quantitative analysis of a large number of metabolites is increasing our knowledge of how complex metabolic networks interact and how they are dynamically modified under stress adaptation and tolerance processes. A vast amount of research has been done using metabolomic approaches to (i) characterize metabolic responses to abiotic stress, (ii) to discover novel genes and annotate gene function, and, (iii) more recently, to identify metabolic quantitative trait loci. The integration of the collected metabolic data concerning abiotic stress responses is helping in the identification of tolerance traits that may be transferable to cultivated crop species. In this review, the diverse metabolic responses identified in plants so far are discussed. We also include recent advances in the study of plant metabolomes and metabolic fluxes with a focus on abiotic stress-tolerance trait interactions.

Conserved versatile master regulators in signalling pathways in response to stress in plants

Environmental conditions have forced plants to develop elaborated molecular strategies to surpass natural obstacles to growth and proliferation. Elements in multiple signaling cascades allow plants to sense multiple and simultaneous ambient cues, and establish an opportune defensive response. A group of versatile master regulators of gene expression are decisive to control plant responses to stressing conditions. For crop breeding purposes, the task is to determine how to activate these key regulators to enable accurate and optimal responses to stressing conditions. In this review, we discuss how and which master regulators are implied in the responses to biotic and stresses, their evolution in the life kingdoms, and the interaction with other molecular factors that lead to a proper and efficient plant response.

The 5S rRNA is associated with Ro60 ribonucleoprotein and is co-precipitated with hYRNAs by anti-Ro antibodies.

Ro particles are conserved molecules that contain a YRNA and various Ro proteins, which are recognized by autoimmune sera from patients with lupus erythematosus or Sjögrens syndrome. The Ro60 ribonucleoprotein (RNP) forms complexes with certain 5S rRNAs, in such a manner that Ro60 could participate in the control of 5S rRNA production. The present studies were carried out to explore the interaction of Ro components, and to address the question whether Ro60 RNP binds simultaneously 5S rRNA and hYRNA. Anti-Ro60 antibodies were used to immunoprecipitate the RNA. Immunoprecipitates were reverse transcribed with specific oligonucleotides and the resulting cDNAs from 5S and hY4 were amplified by PCR. We found that 5S rRNA is complexed with hY4 and hY5 RNAs by means of the Ro60 RNP. Moreover, by in situ hybridization assays we were able to demonstrate that these molecules have a similar nuclear distribution. According to these results, it seems reasonable to assume that the Ro60 protein could be involved in ribosome assembly.

Draft genome sequence of Bacillus velezensis 2A-2B strain: a rhizospheric inhabitant of Sporobolus airoides (Torr.) Torr . , with antifungal activity against root rot causing phytopathogens

A Bacillus velezensis strain from the rhizosphere of Sporobolus airoides (Torr.) Torr., a grass in central-north México, was isolated during a biocontrol of phytopathogens scrutiny study. The 2A-2B strain exhibited at least 60% of growth inhibition of virulent isolates of phytopathogens causing root rot. These phytopathogens include Phytophthora capsici, Fusarium solani, Fusarium oxysporum and Rhizoctonia solani. Furthermore, the 2A-2B strain is an indolacetic acid producer, and a plant inducer of PR1, which is an induced systemic resistance related gene in chili pepper plantlets. Whole genome sequencing was performed to generate a draft genome assembly of 3.953xa0MB with 46.36% of GC content, and a N50 of 294,737. The genome contains 3713 protein coding genes and 89 RNA genes. Moreover, comparative genome analysis revealed that the 2A-2B strain had the greatest identity (98.4%) with Bacillus velezensis.