Stress induced acquisition of somatic embryogenesis in common bean Phaseolus vulgaris L.

Common bean Phaseolus vulgaris L. has been shown to be a recalcitrant plant to induce somatic embryogenesis (SE) under in vitro conditions. We used an alternative strategy to induce SE in common bean based upon the use of a cytokinin (BAP) coupled with osmotic stress adaptation instead of SE response that is induced by auxins. Explants derived from zygotic embryos of common bean were subjected to osmotic stress (sucrose 12 % w/v, 0.5 M) in the presence of BAP 10 mg/L and adenine free base 40 mg/L to induce somatic embryos from specific competent cells of the apical meristem and cotyledonary node. Somatic embryos were obtained from the competent cells in a direct response (direct SE). In a secondary response (secondary SE), those somatic embryos formed proembryogenic masses (PEM) that originated/developed into secondary somatic embryos and showed the SE ontogeny. Maturation of somatic embryos was achieved by using different osmolality media and converted to plants. Full-visible light spectrum was necessary to achieve efficient plant regeneration. Long-term recurrent SE was demonstrated by propagation of PEM at early stages of SE. This protocol is currently being applied for stable genetic transformation by means of Agrobacterium tumefaciens and bioballistics as well as for basic biochemical and molecular biology experiments.

The capsicum transcriptome DB: a "hot" tool for genomic research.

Chili pepper (Capsicum annuum) is an economically important crop with no available public genome sequence. We describe a genomic resource to facilitate Capsicum annuum research. A collection of Expressed Sequence Tags (ESTs) derived from five C. annuum organs (root, stem, leaf, flower and fruit) were sequenced using the Sanger method and multiple leaf transcriptomes were deeply sampled using with GS-pyrosequencing. A hybrid assembly of 1,324,516 raw reads yielded 32,314 high quality contigs as validated by coverage and identity analysis with existing pepper sequences. Overall, 75.5% of the contigs had significant sequence similarity to entries in nucleic acid and protein databases; 23% of the sequences have not been previously reported for C. annuum and expand sequence resources for this species. A MySQL database and a user-friendly Web interface were constructed with search-tools that permit queries of the ESTs including sequence, functional annotation, Gene Ontology classification, metabolic pathways, and assembly information. The Capsicum Transcriptome DB is free available from http://www.bioingenios.ira.cinvestav.mx:81/Joomla/

The global arginine regulator ArgR controls expression of argF in Pseudomonas syringae pv. phaseolicola but is not required for the synthesis of phaseolotoxin or for the regulated expression of argK.

In Pseudomonas syringae pv. phaseolicola the enzyme ornithine carbamoyltransferase (OCTase), encoded by argF, is negatively regulated by argR, similar to what has been reported for Pseudomonas aeruginosa. However, production of the phaseolotoxin-resistant OCTase encoded by argK, synthesis of phaseolotoxin, and infectivity for bean pods occur independently of the ArgR protein.