Species-specific acquisition and consolidation of long-term memory in parasitic wasps.
Long-term memory (LTM) formation usually requires repeated, spaced learning events and is achieved by the synthesis of specific proteins. Other memory forms require a single learning experience and are independent of protein synthesis. We investigated in two closely related parasitic wasp species, Cotesia glomerata and Cotesia rubecula, whether natural differences in foraging behaviour are correlated with differences in LTM acquisition and formation. These parasitic wasp species lay their eggs in young caterpillars of pierid butterflies and can learn to associate plant odours with a successful egg laying experience on caterpillars on the odour-producing plant. We used a classical conditioning set-up, while interfering with LTM formation through translation or transcription inhibitors. We show here that C. rubecula formed LTM after three spaced learning trials, whereas C. glomerata required only a single trial for LTM formation. After three spaced learning trials, LTM formation was complete within 4 h in C. glomerata, whereas in C. rubecula, LTM formation took 3 days. Linking neurobiology with ecology, we argue that this species-specific difference in LTM acquisition and formation is adaptive given the extreme differences in both the number of foraging decisions of the two wasp species and in the spatial distributions of their respective hosts in nature. (+info)
A gene from the cellulose synthase-like C family encodes a beta-1,4 glucan synthase.
Despite the central role of xyloglucan (XyG) in plant cell wall structure and function, important details of its biosynthesis are not understood. To identify the gene(s) responsible for synthesizing the beta-1,4 glucan backbone of XyG, we exploited a property of nasturtium (Tropaeolum majus) seed development. During the last stages of nasturtium seed maturation, a large amount of XyG is deposited as a reserve polysaccharide. A cDNA library was produced from mRNA isolated during the deposition of XyG, and partial sequences of 10,000 cDNA clones were determined. A single member of the C subfamily from the large family of cellulose synthase-like (CSL) genes was found to be overrepresented in the cDNA library. Heterologous expression of this gene in the yeast Pichia pastoris resulted in the production of a beta-1,4 glucan, confirming that the CSLC protein has glucan synthase activity. The Arabidopsis CSLC4 gene, which is the gene with the highest sequence similarity to the nasturtium CSL gene, is coordinately expressed with other genes involved in XyG biosynthesis. These and other observations provide a compelling case that the CSLC gene family encode proteins that synthesize the XyG backbone. (+info)
Structural evidence for the evolution of xyloglucanase activity from xyloglucan endo-transglycosylases: biological implications for cell wall metabolism.
High-resolution, three-dimensional structures of the archetypal glycoside hydrolase family 16 (GH16) endo-xyloglucanases Tm-NXG1 and Tm-NXG2 from nasturtium (Tropaeolum majus) have been solved by x-ray crystallography. Key structural features that modulate the relative rates of substrate hydrolysis to transglycosylation in the GH16 xyloglucan-active enzymes were identified by structure-function studies of the recombinantly expressed enzymes in comparison with data for the strict xyloglucan endo-transglycosylase Ptt-XET16-34 from hybrid aspen (Populus tremula x Populus tremuloides). Production of the loop deletion variant Tm-NXG1-DeltaYNIIG yielded an enzyme that was structurally similar to Ptt-XET16-34 and had a greatly increased transglycosylation:hydrolysis ratio. Comprehensive bioinformatic analyses of XTH gene products, together with detailed kinetic data, strongly suggest that xyloglucanase activity has evolved as a gain of function in an ancestral GH16 XET to meet specific biological requirements during seed germination, fruit ripening, and rapid wall expansion. (+info)
Fructobacillus tropaeoli sp. nov., a fructophilic lactic acid bacterium isolated from a flower.