plant-growth-agrobacterium-mediated-floral-dip-transformation

Plant Growth and Agrobacterium-mediated Floral-dip Transformation of the Extremophyte <em>Schrenkiella parvula</em>

Schrenkiella parvula is an extremophyte adapted to various abiotic stresses, including multiple ion toxicity stresses. Despite high-quality genomic ...

Louisiana State University

Many bacteria encode biosynthetic proteins that produce a vast array of natural products. These compounds are often synthesized during host invasion as they function as virulence factors. In addition, such secondary metabolites have yielded numerous molecular scaffolds with pharmaceutical and clinical importance. The gene clusters that encode proteins responsible for synthesis of these compounds are typically silenced or "cryptic" under laboratory growth conditions, hampering discovery of novel lead compounds. We report here that MftR is a global repressor of secondary metabolite synthesis in Burkholderia thailandensis and that urate functions as a physiologically relevant inducer of gene expression. Biosynthetic gene clusters under MftR control include those associated with production of the antimicrobial bactobolins, the iron siderophore malleobactin, and the virulence factor malleilactone. MftR also controls additional genes associated with survival in a host environment, such as genes encoding components of the type III secretion system (T3SS) and proteins linked to anaerobic respiration. This observation not only has implications for understanding activation of gene regulatory networks during host invasion, but it also paves the way for isolation of novel therapeutic leads.

Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis.

The H2A.Z histone variant plays a role in the modulation of environmental responses, but the nature of the associated mechanisms remains enigmatic. We investigated global H2A.Z deposition and transcriptomic changes in rice (Oryza sativa) upon exposure to phosphate (Pi) deficiency and in response to RNAi knockdown of OsARP6, which encodes a key component of the H2A.Z exchange complex. Both Pi deficiency and OsARP6-knockdown resulted in similar, profound effects on global H2A.Z distribution. H2A.Z in the gene body of stress-responsive genes was negatively correlated with gene expression, and this was more apparent in response to Pi deficiency. In contrast, the role of H2A.Z at the transcription start site (TSS) was more context dependent, acting as a repressor of some stress-responsive genes, but an activator of some genes with housekeeping functions. This was especially evident upon OsARP6-knockdown, which resulted in down-regulation of a number of genes linked to chloroplast function that contained decreases in H2A.Z at the TSS. Consistently, OsARP6-RNAi plants exhibited lower chlorophyll content relative to the wild-type. Our results demonstrate that gene body-localized H2A.Z plays a prominent role in repressing stress-responsive genes under non-inductive conditions, whereas H2A.Z at the TSS functions as a positive or negative regulator of transcription.

Rice H2A.Z negatively regulates genes responsive to nutrient starvation but promotes expression of key housekeeping genes.

Seedling establishment in an extreme environment requires an integrated genomic and physiological response to survive multiple abiotic stresses. The extremophyte, Haloxylon ammodendron is a pioneer species capable of colonizing temperate desert sand dunes. We investigated the induced and basal transcriptomes in H. ammodendron under water-deficit stress during early seedling establishment. We find that not only drought-responsive genes, but multiple genes in pathways associated with salt, osmotic, cold, UV, and high-light stresses were induced, suggesting an altered regulatory stress response system. Additionally, H. ammodendron exhibited enhanced biotic stress tolerance by down-regulation of genes that were generally up-regulated during pathogen entry in susceptible plants. By comparing the H. ammodendron basal transcriptome to six closely related transcriptomes in Amaranthaceae, we detected enriched basal level transcripts in H. ammodendron that shows preadaptation to abiotic stress and pathogens. We found transcripts that were generally maintained at low levels and some induced only under abiotic stress in the stress-sensitive model, Arabidopsis thaliana to be highly expressed under basal conditions in the Amaranthaceae transcriptomes including H. ammodendron. H. ammodendron shows coordinated expression of genes that regulate stress tolerance and seedling development resource allocation to support survival against multiple stresses in a sand dune dominated temperate desert environment.

Article	Year
Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis. ACS chemical biology\| PubMed ID: 29087175	2017
Rice H2A.Z negatively regulates genes responsive to nutrient starvation but promotes expression of key housekeeping genes. Journal of experimental botany\| PubMed ID: 29955860	2018
Transcriptomic view of survival during early seedling growth of the extremophyte Haloxylon ammodendron. Plant physiology and biochemistry : PPB\| PubMed ID: 30292980	2018

Guannan Wang

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