Structure and diversification of the bovine immunoglobulin repertoire

Our understanding of the basis to immunoglobulin formation in cattle has benefited substantially from the application of molecular biology over the past decade. It is now established that both the lambda light chain and heavy chain repertoires are founded upon the frequent expression of single gene families and subgroups of segments which are of conserved sequence. It is likely that a functional kappa locus exists in the bovine genome but this isotype comprises as few as 5% of bovine light chains. Similarly, alternative but non-expressed V(H) gene families are present posing intriguing but unresolved questions about the regulation of immunoglobulin synthesis. The heavy chain frequently bears a third complementarity-determining region which is atypically long but the processes which expand this region of the reading frame and its contribution to the interaction with antigen remain matters of speculation. Opportunities exist to map the major immunoglobulin loci and to define the membership and sequence diversity of the gene families which dominate each repertoire. However, it is already evident that cattle cannot generate significant diversity from rearrangement and junctional imprecision alone. Elucidation of the mechanism(s), dynamics and tissue distribution of immunoglobulin diversification in cattle, thus, remain key challenges in this branch of veterinary immunology.     

Preference and performance of <Emphasis Type="Italic">Plutella xylostella</Emphasis> (L.) (Lepidoptera: Plutellidae) on canola cultivars

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is an important insect pest of canola, Brassica napus L., in Ardabil, Iran. Host plant resistance is an essential component of integrated management of P. xylostella. We investigated the preferences and performance of P. xylostella on nine commercial cultivars of canola, namely Zarfam, RGS003, Adder, Okapi, Opera, Hyola401, Ebonite Option500 and Elite under greenhouse conditions at 23 ± 1°C, 50 ± 5% RH and 14L:10D. In free-choice situation, oviposition was lowest on Opera (23.5) and highest on Zarfam (44.7). In the life table study, fecundity of new generation female moths was lowest on Opera (95.4) and highest on Adder (145.7). Survival from egg to adult was significantly lower on Opera, Option500 and Hyola401 than on other tested cultivars. The intrinsic rate of natural increase (r _m) and population growth rate (λ) were lowest on Opera and highest on Zarfam. The generation time (T) was shortest on Zarfam (17.2 days) and longest on Hyola401 (19.9 days) whereas doubling time (DT) was longest on Opera (3.9 days) and shortest on Zarfam (3.0 days). Our results clearly suggest that Opera was the most resistant host among the tested cultivars and has the potential to be used in the integrated management of P. xylostella.     

蚕品种选育多用途化发展趋势

为了满足蚕桑生产发展多元化和提升改造传统蚕桑业发展需要开展的特殊用途蚕品种选育进展迅速,本文就以蚕丝生产为目的如雄蚕品种、细纤度蚕品种、粗纤度蚕品种、人工饲料育品种及广食性蚕品种、天然彩色茧蚕品种等的选育,以及非蚕丝生产为目的如吐平面丝蚕品种、吐丝胶茧蚕品种、生物反应器专用蚕品种、药食专用蚕品种等育种研究进展进行概述.     

Zoospore chemotaxis of closely related legume‐root infecting Phytophthora species towards host isoflavones

Phytophthora niederhauserii, P. pisi, P. sojae and P. vignae are closely related species that are pathogenic to various legume plants. While P. sojae and P. vignae are reported to specifically infect soybean and cowpea, respectively, P. pisi is reported to attack pea and faba bean. Phytophthora niederhauserii is considered to have a broad host range. Zoospores of some Phytophthora species are chemotactically attracted to the isoflavones that are secreted by their host plants. The focus of the current study was to determine the chemotaxic behaviour of zoospores from closely related legume‐root infecting Phytophthora species and to investigate the correlation, if any, to host preference as determined by greenhouse pathogenicity tests. The results showed that P. sojae and P. vignae were attracted to the non‐soybean isoflavone prunetin as well as to the soybean isoflavones genistein and daidzein, which is in contrast with their host specificity on soybean and cowpea, respectively. On the other hand, P. pisi and P. niederhauserii were only attracted to prunetin, previously reported to be produced by pea, but not to the isoflavones associated with the non‐host soybean. The lack of responsiveness to genistein and daidzein in P. pisi may represent a recent adaptation to the host specialization towards pea. However, the affinity of P. niederhauserii to prunetin shows that this trait can also be present in taxa not specifically associated with legume hosts.