Genotypic response of cowpea Vigna unguiculata (L.) to in vitro regeneration from cotyledon explants

Summary A plant regeneration system applicable to 17 cowpea genotypes was developed. Cotyledons were initiated on 1/3 MS medium containing 15 to 35 mg N⁶-benzyladenine (BA) per 1 (66.6 to 155.3 μM) for 5 to 15 d. For shoot regeneration, the explants were transferred to a medium containing 1 mg BA per 1 (4.4 μM). Within 1 wk, shoot formation was visible at the proximal end of the cotyledons. Regeneration percentages (1% to 11%) and the numbers of shoots (4 to 12 per explant) were significantly influenced by genotype. Culture duration and BA concentration in the initiation stage significantly affected regeneration capacity. Explants initiated on media containing 15 mg BA per 1 for 5 d resulted in the highest percentage of explants capable of regeneration. Conversely, the highest number of shoots was obtained from explants initiated on media supplemented with 35 mg BA per 1. Whole plants were obtained on a plant growth regulator-free medium. To our knowledge, this is the first report of plant regeneration from U.S. commercial cowpea cultivars and breeding lines. This system is adaptable to diverse cowpea genotypes and will facilitate cowpea genetic transformation. Published with the approval of the Director of the Arkansas Agricultural Experiment Station.     

Non-right sidedness: an association with lower IL-2 production.

Using a laterality questionnaire, 138 normal healthy individuals were classified as right-sided and 25 as non-right sided. Interleukin-2 (IL-2) was generated from whole blood obtained from these subjects using mitogen (PHA) stimulation. IL-2 was quantitated in picograms/ml using an enzyme immunoassay (ELISA). Additionally, sera from these subjects were tested for 7 autoantibodies by standard serological methods. As compared to right sided subjects, non-right sided individuals had significantly lower IL-2 production. Non-right sided individuals with autoantibodies had significantly lower IL-2 production than right sided subjects with or without autoantibodies, but did not differ significantly from their non-right sided counterparts without autoantibodies. These data support the increasing evidence for the differential and lateralized regulation of immune functions by the right and left cerebral regions.     

Ethylene inhibitors promote in vitro regeneration of cowpea (Vigna unguiculata L.)

Summary Ethylene is a plant growth regulator that is known to influence in vitro morphogenesis. This study investigated the effects of three ethylene inhibitors, silver nitrate (AgNO₃), 2,5-norbornadiene, and cobalt chloride (CoCl₂), on the regeneration of cowpea from cotyledon explants. Significant increases in the percentage of regeneration occurred as a result of adding either 50 μM AgNO₃ or 100 μM 2,5-norbornadiene. The number of shoots produced per explant was enhanced by adding 25 μM CoCl₂ or 100 μM norbornadiene. Maximum shoot elongation was obtained with 25 μM of either CoCl₂ or norbornadiene. The effect of the duration of exposure to AgNO₃ was also determined. The greatest percent regeneration was obtained with the addition of 60 μM AgNO₃ either to both the initiation and regeneration stages, or to only the regeneration stage. The promotive effects on organogenesis in response to ethylene inhibitors suggests an important role for ethylene in the process of in vitro morphogenesis of cowpea and may contribute to its normally low regeneration frequency.     

Salicylic acid induces amelioration of chromium toxicity and affects antioxidant enzyme activity in Sorghum bicolor L.

Aim: Chromium (Cr(VI)) would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. Cr(VI) toxicity is often associated with oxidative stress, caused by the excessive formation of reactive oxygen species (ROS). In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM) toxicity. Salicylic acid (SA) plays a key role in the signal transduction pathways of various stress responses, demonstrating the protective effect of SA against abiotic stress factors. So, the present investigation was carried out to study the amelioration of pernicious effects of different concentration of Cr(VI) (0.0, 2.0, and 4.0?mg Cr(VI) kg^?1 soil in the form of potassium dichromate) by treatments of salicylic acid solution viz. pretreatment and foliar spray via antioxidative enzymes and their metabolites.

Results: With different treatments of salicylic acid solution, the reinstatement from ill effects of Cr(VI) toxicity was contemplated but the most conspicuous effect was observed when salicylic acid solution was supplied through the foliar spray (0.50?mM). This was accompanied with an increase in ascorbate peroxidase activity and hydrogen peroxide content and decrease in peroxidase activity and ascorbic acid content.

Significance of the study: This study suggests that salicylic acid when applied through pre-treatment of seeds or through a foliar spray can be used to ameliorate the toxic effects of chromium (VI). Salicylic acid has the great potential for reducing the toxicity of heavy metals without negatively impacting the growth of the plants.     

The Genome Sequence of the Fungal Pathogen Fusarium virguliforme That Causes Sudden Death Syndrome in Soybean

Fusarium virguliforme causes sudden death syndrome (SDS) of soybean, a disease of serious concern throughout most of the soybean producing regions of the world. Despite the global importance, little is known about the pathogenesis mechanisms of F. virguliforme. Thus, we applied Next-Generation DNA Sequencing to reveal the draft F. virguliforme genome sequence and identified putative pathogenicity genes to facilitate discovering the mechanisms used by the pathogen to cause this disease.

Methodology/Principal Findings

We have generated the draft genome sequence of F. virguliforme by conducting whole-genome shotgun sequencing on a 454 GS-FLX Titanium sequencer. Initially, single-end reads of a 400-bp shotgun library were assembled using the PCAP program. Paired end sequences from 3 and 20 Kb DNA fragments and approximately 100 Kb inserts of 1,400 BAC clones were used to generate the assembled genome. The assembled genome sequence was 51 Mb. The N50 scaffold number was 11 with an N50 Scaffold length of 1,263 Kb. The AUGUSTUS gene prediction program predicted 14,845 putative genes, which were annotated with Pfam and GO databases. Gene distributions were uniform in all but one of the major scaffolds. Phylogenic analyses revealed that F. virguliforme was closely related to the pea pathogen, Nectria haematococca. Of the 14,845 F. virguliforme genes, 11,043 were conserved among five Fusarium species: F. virguliforme, F. graminearum, F. verticillioides, F. oxysporum and N. haematococca; and 1,332 F. virguliforme-specific genes, which may include pathogenicity genes. Additionally, searches for candidate F. virguliforme pathogenicity genes using gene sequences of the pathogen-host interaction database identified 358 genes.

Conclusions

The F. virguliforme genome sequence and putative pathogenicity genes presented here will facilitate identification of pathogenicity mechanisms involved in SDS development. Together, these resources will expedite our efforts towards discovering pathogenicity mechanisms in F. virguliforme. This will ultimately lead to improvement of SDS resistance in soybean.