IN AN D I. CH E T. 1997. Bacillus cereus strain 65, previously isolated as an endophyte of Sinapis, was shown to produce and excrete a chitinase with an apparent molecular mass of 36 kDa. The enzyme was classified as a chitobiosidase because it was able to cleave diacetylchitobiose (GlcNAc) 2 from the non-reducing end of trimeric chitin derivatives. The chitinase exhibited activity over the pH range 4·5-7 5 and was stable between pH 4·0 and 8·5. The enzyme had an isoelectric point of 6·4. Application of B. cereus 65 directly to soil significantly protected cotton seedlings from root rot disease caused by Rhizoctonia solani.

Isolates of different endophytic bacteria were recovered from surface-disinfected seeds obtained from commercial companies, plants in the field and tissue culture. The bacteria were isolated from seeds after stringent surfacedisinfection. Pseudomonas fluorescens (isolate no. 14) from bean inhibited growth of all fungi tested and was fluorescent on King B medium. Bacillus cereus from Sinapis (isolate no. 65) inhibited growth of Rhizoctonia solani, Pythium ultimum and Sclerotium rolfsii and also exhibited chitinase activity. Bacillus subtilis from onion tissue culture (isolate no. 72) inhibited R. solani and P. ultimum growth. B. cereus from cauliflower (isolate no. 78) inhibited growth of R. sotani. B. pumilus from sunflower (isolate no. 85) inhibited growth of R. solani and S. rolfsii. B. cereus (isolate no. 65) was introduced into cotton, and by using radioactive labelling we found that it was present for 16 days in the root-stem junction. It is most likely that these bacteria were still found 72 days after their introduction in the root and stem, at levels of 2.8.105 and 5.104 cfu g-1 fresh weight, respectively, when selective medium was used. There was no difference between control and treated plants in their height or in the fresh weight of roots, stems and leaves.When cotton seedlings were inoculated with B. cereus (isolate no. 65), B. subtilis (isolate no. 72) or B. pumilus (isolate no. 85), disease incidence caused by Rhizoctonia solani was reduced in the greenhouse by 51%, 46% and 56%, respectively. In bean seedlings inoculated with B. subtilis (isolate no. 72), B. cereus (isolate no. 78) or B. pumilus (isolate no. 65), disease incidence caused by Sclerotium rolfsii was reduced by 72%, 79% and 26%, respectively, as compared to control. In both cotton and bean seedlings, these endophytes reduced the disease index more than 50%. These results indicate that endophytic bacteria can survive inside cotton plants and are efficient agents for biological control against plant pathogens under greenhouse conditions.

MEKs, which operate within the ERK cascade, shuttle into the nucleus, but are rapidly exported from this location, forming an apparent cytosolic distribution both before and after stimulation. Two dierent mechanisms have been proposed for the nuclear translocation of MEKs. One of them involves a constant and nonregulated shuttling of MEKs into the nucleus operating both before and after mitogenic stimulation. The other mechanism seems to require the activity of MEKs and is facilitated in response to mitogenic stimulation. Here we show that these two mechanisms may coexist in the same cells. We found that leptomycin B (LMB), a potent inhibitor of nuclear export, induces a nuclear accumulation of MEKs, and this was signi®cantly facilitated by stimulation of LMB-treated cells with EGF, TPA and peroxovanadate. The EGF-stimulated, but not the LMBinduced translocation was attenuated by MEK inhibitors and by using inactive forms of MEK1. We also show that LMB slightly activates the ERK cascade, but this activity only partially induces the nuclear accumulation of MEKs in cells treated by LMB alone. Thus, MEKs translocate into the nucleus by a combination of nonregulated and stimulated processes that contribute to the nuclear translocation of MEKs either in resting cells or upon mitogenic stimulation. Oncogene (2001) 20, 7588 ± 7596.

Enterobacter cloacae was found to be associated with the pollen of several Mediterranean pines. The bacterium was detected only in mature pollen of Pinus halepensis, P. brutia, and P. pinea. E. cloacae is considered to be an obligatory endophyte based on its occurrence in disinfected male cones and the successful inoculation of seedlings of the above 3 species with E. cloacae AS1 isolated from pollen of P. halepensis used as a model strain. Strain AS1 was able to produce indolyl-3-acetic acid (IAA) from L-tryptophan in culture, and this was probably the source of the increased IAA content in the germination medium of pollen. In addition, strain AS1 promoted adventitious root formation in mung bean (Vigna radiata) cuttings. However, it was not possible to obtain bacterium-free pollen to elucidate its role in pollen germination.

An accurate method is described for evaluating the relative effectiveness of isolates ofFusarium avenaceumas potential biological control agents for weeds such as spotted knapweed and wild oat. The method uses seeds that have been disinfected, placed in tubes containing water agar, and challenged with various isolates ofF. avenaceum.Evaluatory data on the pathogenicity of the fungi are obtained after 14 d, when plants and fungi both are grown on water agar in the lab. Commonly, potential biocontrol agents are tested on seeds placed in the soil, but up to 60 d may be required for results. However, comparative studies using the soil test vs. the water agar test indicated that the water agar tests are giving comparable results to those from greenhouse tests but in a shorter time (14 vs. 60 d). Also, both water agar and soil tests were done with a number of crop plants including wheat, barley, alfalfa, and wild oat with comparable results. Thus, this method has the potential to screen many pathogens that may have potential biocontrol activities in a short time.