Functional and regulatory conservation of the soybean ER stress-induced DCD/NRP-mediated cell death signaling in plants.

Background: The developmental and cell death domain (DCD)-containing asparagine-rich proteins (NRPs) were first identified in soybean (Glycine max) as transducers of a cell death signal derived from prolonged endoplasmic reticulum (ER) stress, osmotic stress, drought or developmentally-programmed leaf senescence via the GmNAC81/GmNAC30/GmVPE signaling module. In spite of the relevance of the DCD/NRP-mediated signaling as a versatile adaptive response to multiple stresses, mechanistic knowledge of the pathway is lacking and the extent to which this pathway may operate in the plant kingdom has not been investigated.

Results: Here, we demonstrated that the DCD/NRP-mediated signaling also propagates a stress-induced cell death signal in other plant species with features of a programmed cell death (PCD) response.

The molecular chaperone binding protein BiP prevents leaf dehydration-induced cellular homeostasis disruption.

BiP overexpression improves leaf water relations during droughts and delays drought-induced leaf senescence. However, whether BiP controls cellular homeostasis under drought conditions or simply delays dehydration-induced leaf senescence as the primary cause for water stress tolerance remains to be determined. To address this issue, we examined the drought-induced transcriptomes of BiP-overexpressing lines and wild-type (WT) lines under similar leaf water potential (ψw) values.

The endoplasmic reticulum binding protein BiP displays dual function in modulating cell death events.

The binding protein (BiP) has been demonstrated to participate in innate immunity and attenuate endoplasmic reticulum- and osmotic stress-induced cell death. Here, we employed transgenic plants with manipulated levels of BiP to assess whether BiP also controlled developmental and hypersensitive programmed cell death (PCD). Under normal conditions, the BiP-induced transcriptome revealed a robust down-regulation of developmental PCD genes and an up-regulation of the genes involved in hypersensitive PCD triggered by nonhost-pathogen interactions.

The ER luminal binding protein (BiP) mediates an increase in drought tolerance in soybean and delays drought-induced leaf senescence in soybean and tobacco.

The ER-resident molecular chaperone BiP (binding protein) was overexpressed in soybean. When plants growing in soil were exposed to drought (by reducing or completely withholding watering) the wild-type lines showed a large decrease in leaf water potential and leaf wilting, but the leaves in the transgenic lines did not wilt and exhibited only a small decrease in water potential. During exposure to drought the stomata of the transgenic lines did not close as much as in the wild type, and the rates of photosynthesis and transpiration became less inhibited than in the wild type.

Antibiosis by Bacillus amyloliquefaciens ribonuclease barnase expressed in Escherichia coli against symbiotic and endophytic nitrogen-fixing bacteria.

A modified antibiosis assay was used to evaluate growth inhibition of symbiotic and endophytic bacteria by E. coli strains producing Bacillus amyloliquefaciens ribonuclease, barnase. Inhibition zones were only observed when the assays were performed in minimal medium agar.

A new system to control the barnase expression by a NifA-dependent promoter.

Barnase is a potent ribonuclease widely used as a cytotoxic agent, tightly regulated by barstar to maintain cell viability. In this report, we describe a new composite regulatory system to control barnase cytotoxicity and expression, involving barstar and lacI genes under control of the NifA-, sigma54-dependent Sinorhizobium meliloti nifH promoter, and the barnase gene under control of the LacI-repressible ptac promoter. In this system, expression of thenifH promoter, activated by constitutively expressed NifA, resulted in constitutive synthesis of the LacI and barstar proteins.

Monitoring Azospirillum-wheat interactions using the gfp and gusA genes constitutively expressed from a new broad-host range vector.

To monitor the colonization of wheat roots by Azospirillum brasilense, we constructed several plasmids based on the pBBR1 replicon expressing the gfp and gusA genes constitutively. Both genes were placed under control of the gentamycin resistance gene promoter resulting in high levels of expression in Escherichia coli and A. brasilense.