Extreme specificity of NCR gene expression in Medicago truncatula.

Background: Legumes form root nodules to house nitrogen fixing bacteria of the rhizobium family. The rhizobia are located intracellularly in the symbiotic nodule cells. In the legume Medicago truncatula these cells produce high amounts of Nodule-specific Cysteine-Rich (NCR) peptides which induce differentiation of the rhizobia into enlarged, polyploid and non-cultivable bacterial cells.

Genomic organization and evolutionary insights on GRP and NCR genes, two large nodule-specific gene families in Medicago truncatula.

Deciphering the mechanisms leading to symbiotic nitrogen-fixing root nodule organogenesis in legumes resulted in the identification of numerous nodule-specific genes and gene families. Among them, NCR and GRP genes encode short secreted peptides with potential antimicrobial activity. These genes appear to form large multigenic families in Medicago truncatula and other closely related legume species, whereas no similar genes were found in databases of Lotus japonicus and Glycine max.

Arabidopsis RNA-binding protein UBA2a relocalizes into nuclear speckles in response to abscisic acid.

The Arabidopsis thaliana RNA binding protein UBA2a is the closest homologue of the Vicia faba AKIP1 (56% identity). Like AKIP1, UBA2a is a constitutively-expressed nuclear protein and in response to ABA it is also reorganized within the nucleus in "speckles" suggesting a possible role of this protein in the regulation of mRNA metabolism during ABA signaling. AKIP1 interacts with, and is phosphorylated by, the upstream ABA-activated protein kinase AAPK.

Use of infrared thermal imaging to isolate Arabidopsis mutants defective in stomatal regulation.

In response to drought, plants synthesise the hormone abscisic acid (ABA), which triggers closure of the stomatal pores. This process is vital for plants to conserve water by reducing transpirational water loss. Moreover, recent studies have demonstrated the advantages of the Arabidopsis stomatal guard cell for combining genetic, molecular and biophysical approaches to characterise ABA action.