Treatment of pea pods with Bruchin B results in up-regulation of a gene similar to MtN19.

Differential display was used to examine changes in gene expression that resulted from treatment of pea (Pisum sativum L.) with Bruchin B. This lipid-derived regulator, one of several closely related compounds collectively referred to as bruchins, is an insect elicitor that causes localized cell division and callus formation when applied to pods of pea and certain other legumes. A DNA fragment that was prominently displayed after bruchin treatment was cloned and sequenced, and a full-length cDNA was obtained. This cDNA exhibited a high degree of sequence similarity to a gene, MtN19, expressed in root nodules of Medicago truncatula Gaertn. MtN19 codes for a putative protein of unknown function that is similar in sequence to predicted proteins from a number of other plant species, both leguminous and non-leguminous. Quantitative real-time PCR showed that the expression of this MtN19-like gene was significantly up-regulated within 1.5 h of bruchin treatment, and increased more than 100-fold within 6 h of treatment. Given the rapid and strong up-regulation after exposure of pods to a bruchin, it is likely that this gene plays an important role in the response of pea to these insect elicitors.

Melanin in the extracellular matrix of germlings of Botrytis cinerea.

Previous work on the composition of the extracellular matrix of germlings of the plant pathogenic fungus Botrytis cinerea demonstrated the presence of carbohydrate, protein, and simple lipids; which, together, comprised 50-60% of the dry weight. Here we show that most of the remaining mass of the extracellular matrix consists of a chemically inert dark pigment with the electron paramagnetic resonance characteristics of a melanin. Scanning electron micrographs of the purified pigment, and transmission electron micrographs of thin sections made using the pigment indicate that it has a filamentous structure. We conclude that melanin is an important component of the extracellular matrix of germlings of B. cinerea. This is the first report of a melanin present in the extracellular matrix of a plant pathogenic fungus.

Bruchins, plant mitogens from weevils: structural requirements for activity.

Bruchins are 3-hydroxypropanoate esters of long-chain alpha,omega-diols from pea weevils and cowpea weevils that have been shown to initiate callus formation on pea pods at extremely low application rates. Synthetic analogs have been prepared and examined to evaluate structural requirements for inducing this unusual neoplastic response. Chain length (optimum length C22-C24) is important, whereas unsaturation within the chain is relatively unimportant. Difunctionality is required for maximum activity, but the alpha,omega-diols themselves are inactive. Most critical is the ester portion(s) of the molecules; 3-hydroxypropanoate esters are far more active than any analogs examined.

A PCR-Based Technique for Detection of Neotyphodium Endophytes in Diverse Accessions of Tall Fescue.

A previously described polymerase chain reaction (PCR)-based method used for detection of Neotyphodium coenophialum in tall fescue detected Neotyphodium endophytes in some, but not all, infected plants from a geographically diverse sample. In the study reported here, a different set of primers, based on intervening sequences of the tubulin 2 gene, were prepared and used for PCR. PCR with these primers yielded the expected 444 base pair amplification product with DNA from 104 of the 106 infected accessions tested. In addition, one accession originally scored as endophyte-free on the basis of a tissue culture test was correctly rated as endophyte-infected using the PCR procedure. Results suggest that primers based on intervening sequences of the tubulin 2 gene can be used for PCR-based detection of Neotyphodium endophytes in tall fescue accessions of diverse origin.