A novel MYB transcription factor CaPHL8 provide clues about evolution of pepper immunity againstsoil borne pathogen.

MYB TFs in plants are of crucial importance not only for growth and development but also for plant defense against pathogens. CaPHL8, an MYB TF, was identified as a positive regulator of pepper defense against Ralstonia solanacerum inoculation (RSI). Phylogenetic evaluation and functional characterization of CaPHL8 revealed its role in pepper defense evolution. Analysis of the amino acid sequence of PHL8 demonstrates its maximum similarity with the MYB family transcription factor in other plants. Up-regulation of CaPHL8 was observed in pepper plants facing Ralstonia attack.. Consistently the GUS activity of pCaPHL8 showed significantly high activity under RSI as compared to mock-treated plants. The loss of function studies of CaPHL8 conducted through VIGS (virus-induced gene silencing) confirmed the reduced pepper immunity to R. solanacearum and impaired plant growth accompanied by high pathogen growth. Compromised pepper immunity in silenced plants was coupled with a reduction in transcription of defense linked marker genes. On the other hand, transiently overexpressing CaPHL8 (35S::CaPHL8-HA) in pepper caused a hypersensitive response, elevated H2O2 production and high expression of immunity associated marker genes. Stable expression of CaPHL8-HA protein was confirmed by Western blot. Additionally, unlike many other TFs, CaPHL8 is not involved in high-temperature stress tolerance as evident by phenotype and non-significant transcription of high temperature-tolerance related marker genes in pepper. So, all these findings confirm that CaPHL8 is induced by RSI, not by high temperature and high humidity (HTHH). It provides adaptive plasticity to pepper by activating defense to RSI by direct or indirect regulation of different immunity -associated genes.

Basic leucine zipper domain transcription factors: the vanguards in plant immunity.

Regulation of spatio-temporal expression patterns of stress tolerance associated plant genes is an essential component of the stress responses. Eukaryotes assign a large amount of their genome to transcription with multiple transcription factors (TFs). Often, these transcription factors fit into outsized gene groups which, in several cases, exclusively belong to plants. Basic leucine zipper domain (bZIP) transcription factors regulate vital processes in plants and animals. In plants, bZIPs are implicated in numerous fundamental processes like seed development, energy balance, and responses to abiotic or biotic stresses. Systematic analysis of the information obtained over the last two decades disclosed a constitutive role of bZIPs against biotic stress. bZIP TFs are vital players in plant innate immunity due to their ability to regulate genes associated with PAMP-triggered immunity, effector-triggered immunity, and hormonal signaling networks. Expression analysis of studied bZIP genes suggests that exploration and functional characterization of novel bZIP TFs in planta is helpful in improving crop resistance against pathogens and environmental stresses. Our review focuses on major advancements in bZIP TFs and plant responses against different pathogens. The integration of genomics information with the functional studies provides new insights into the regulation of plant defense mechanisms and engineering crops with improved resistance to invading pathogens. Conclusively, succinct functions of bZIPs as positive or negative regulator mediate resistance to the plant pathogens and lay a foundation for understanding associated genes and TFs regulating different pathways. Moreover, bZIP TFs may offer a comprehensive transgenic gizmo for engineering disease resistance in plant breeding programs.

miRNAs: Major modulators for crop growth and development under abiotic stresses.

Cumulatively, biotic and abiotic stresses of various magnitudes can decrease the production of crops by 70%. miRNAs have emerged as a genetic tool with enormous potential that can be exploited to understand stress tolerance at the molecular level and eventually regulate stress in crops. Plant miRNA targets frequently fit into diverse families of TFs that control the expression of genes related to a certain trait. As key machinery in gene regulatory networks, it is agreed that a broad understanding of miRNAs will greatly increase our understanding of plant responses to environmental stresses. miRNA-led stress regulatory networks are being considered as novel tools for the development of abiotic stress tolerance in crops. At this time, we need to expand our knowledge about the modulatory role of miRNAs during environmental fluctuations. It has become exceedingly clear that with increased understanding of the role of miRNAs during stress, the techniques for using miRNA-mediated gene regulation to enhance plant stress tolerance will become more effective and reliable. In this review we present: (1) miRNAs as a potential avenue for the modulation of abiotic stresses, and (2) summarize the research progress regarding plant responses to stress. Current progress is explained through discussion of the identification and validation of several miRNAs that enhance crop tolerance of salinity, drought, etc., while missing links on different aspects of miRNAs related to abiotic stress tolerance are noted.