Cucurbit biotechnology-the importance of virus resistance

Summary The cucurbit family includes a number of valuable crop species (melon, cucumber, squash/pumpkin, watermelon). Much of this review is concerned with transgenic resistance to viruses, shown to be the major application of biotechnology in the cucurbit family. Progress made with the production of transgenic cucurbit crops is discussed. Published data on field tests of transgenic cucurbits are reviewed, showing that much progress has been made with multiple virus-resistant cucurbit crops which can be productive without chemical control of insect virus vectors. Modes of virus resistance in trangenic cucurbits are discussed, as is the bio-safety of such crops. For the first time a detailed analysis has been made of world-wide and US field test applications for cucurbit crops. World-wide, most field test applications were for melon (54%), followed by squash (32%). World-wide most field test applications were for virus resistance (84%), and most applications (77%) were in the USA. Two transgenic multiple virus-resistant squash crops have been deregulated (released for sale). Additionally, the analysis shows that there are transgenic multiple virus-resistant crops in all major cucurbit species already available, for which several different companies have applied for field tests. This would imply that such crops are ready to be marketed should conditions permit, which would have an impact world-wide in reduction of ecological damage due to chemical control of the insect viral vectors.     

Evaluation of acrylamide grafted moth bean starch as controlled release excipient

The aim of this study was to investigate the applicability of acrylamide grafted moth bean starch as controlled release matrix former. Lamivudine was used as model drug and its controlled release tablets were formulated using various concentration of grafted copolymer. The grafted copolymer was tested for acute toxicity and drug-excipient compatibility study. The formulations were evaluated for physical characteristics like hardness, friability, % drug content and weight variations. The in vitro release study showed that the optimized formulation exhibited highest correlation (R) value in case of Higuchi model and the release mechanism study proved that the formulation showed a combination of diffusion and erosion based release process. There was a significant difference in the pharmacokinetic parameters (T_max, C_max, AUC, V_d, T_1/2 and MDT) of the optimized formulation as compared to the marketed conventional tablet Lamivir^®, which confirmed controlled release potential of acrylamide grafted copolymer.     

The effect of certain exogenous growth regulators on quality of grafted grapevine rootlings

Paclobutrazol (PB), chlormequat (CM), fenarimol (FM), and gibberellin A₃ (GA₃) were applied as exogenous growth regulators once (1 × PB, 1 × CM, 1 × FM, 1 × GA₃), twice (2 × PB, 2 × CM, 2 × FM, 2 × GA3) or three times (3 × PB, 3 × CM, 3 × FM, 3 × GA₃) onto grafted grapevine rootlings of cv. Cardinal on Kober 5BB grown in nursery and in vegetative pots. Water was also applied at each application, at every 15 days, as the control (C). Application treatments 2 × PB and 3 × PB, as well as 2 × CM retarded shoot elongation and increased dry matter content in shoots. Treatments 3 × PB, 2 × CM and 3 × CM also significantly increased dry weight of roots in comparison to C. Repeated application of growth inhibitors (PB and CM) significantly increased starch content in shoots when compared to C as well as to GA₃-treated plants. A very strong correlation existed between the shoot sugar: starch ratio (that was increased by 3 × CM and 2 × PB) and the percentage of first-grade graftlings. PB and CM significantly enhanced maturity (defined here as giving a high rate of survival and reduced post damage) of grapevine graftlings. This is a very important quality attribute for their use as planting material.     

Identification and characterization of proteins that interact with the carboxy terminus of poly(A)-binding protein and inhibit translation in vitro

Poly(A)-binding proteins (PABPs) are multifunctional proteins that play important roles in mRNA stability and protein translation. Two cucumber ( Cucumis sativus L.) proteins, PCI6 (PABP-CT-interacting) and PCI243 were identified based on ability to interact with the carboxy terminus (CT) of PABP in yeast two-hybrid and in vitro binding assays. PCI6 and PCI243 share a conserved amino acid domain (SxLnpnApxFxP) in common with human PABP-CT interactors, and with Arabidopsis ERD15 (early-responsive to dehydration). Deletion analysis and point mutations indicate that presence of this domain is necessary for the interaction, and tests with ERD15 demonstrate that it is predictive of interaction. Other plant proteins possessing this domain fall into two categories: small, acidic proteins like PCI6, PCI243 and ERD15, and larger neutral proteins that also include an RNA recognition motif. PCI6 is expressed in a range of tissues, e.g., leaves, roots, stems and flowers, and follows a diurnal pattern of expression, increasing during light hours and declining overnight. In wheat germ and mouse ascites Krebs-2 in vitro translation systems, PCI6 inhibited translation whereas the non-interacting mutant, PCI6-23A, did not or had a greatly reduced effect. The activity of PCI6, therefore, is reminiscent of that of human PABP-interacting protein 2 (Paip2). These results demonstrate a novel interaction between PABP and several plant proteins sharing a SxLnpxApxFxP motif, with possible implications for translational regulation.     

A mathematical additive model of the structure—activity relationships of gibberellins

By means of a modified Free—Wilson technique, the individual contributions of 22 different substituents on the growth-promoting activity of 67 gibberellins and their synthetic derivatives were estimated for three bioassay systems (dwarf pea, cucumber and lettuce). Statistically significant correlations between the presence of certain structural elements and potency in a given bioassay were observed. The additive character of the contributions is considered in terms of a structural correspondence between a C₁₉-hormone and a specific receptor.     

Deconstructing insect herbivore trivial movement in a monoculture and triculture: Limitations of emigration

Significantly higher population densities of a squash pest beetle, Acalymma vittatum, were observed in a squash monoculture than a triculture of squash, maize, and beans. One hypothesis for such differences is that non-host plants in the triculture cause the herbivore to move more frequently resulting in higher emigration rates from the tricultures. Plant to plant movement of the beetle was studied in vegetative winter squash to evaluate if differences in components of trivial movement would generate a higher emigration rate from the triculture. Tenure times were shorter on plants in the triculture than on plants in the squash monoculture, there was no movement directionality, movement distances were greater in squash monocultures than in tricultures and were greater during July than August. In the tricultures, plant-to-plant transitions were primarily to maize from non-host plants and to beans or squash from host plants during July, but during August, movement from any plant was primarily to maize. We integrated the values of the movement components from vegetative winter squash into a simple Markov model, and found that during July, emigration was estimated to be faster from the triculture than the monoculture, supporting the hypothesis. However, in August, emigration was estimated to be slower from the triculture. In August, maize plants were tall and, by acting like a fence, greatly reduced the movement distance of beetles. The effect of the differences in emigration rate on beetle population density was greatest for small patches, indicating that emigration may be important only in small-scale production systems.     

Argonaute 1 and 5 proteins play crucial roles in the defence against cucumber green mottle mosaic virus in watermelon

RNA silencing, a core part of plants' antiviral defence, requires the ARGONAUTE, DICER-like, and RNA-dependent RNA polymerase proteins. However, how these proteins contribute to watermelon's RNA interference (RNAi) pathway response to cucumber green mottle mosaic virus (CGMMV) has not been characterized. Here, we identify seven ClAGO, four ClDCL, and 11 ClRDR genes in watermelon and analyse their expression profiles when infected with CGMMV. ClAGO1 and ClAGO5 expression levels were highly induced by CGMMV infection. The results of ClAGO1 and ClAGO5 overexpression and silencing experiments suggest that these genes play central roles in watermelon's antiviral defence. Furthermore, co-immunoprecipitation and bimolecular fluorescence complementation experiments showed that ClAGO1 interacts with ClAGO5 in vivo, suggesting that ClAGO1 and ClAGO5 co-regulate watermelon defence against CGMMV infection. We also identified the ethylene response factor (ERF) binding site in the promoters of the ClAGO1 and ClAGO5 genes, and ethylene (ETH) treatment significantly increased ClAGO5 expression. Two ERF genes (Cla97C08G147180 and Cla97C06G122830) closely related to ClAGO5 expression were identified using co-expression analysis. Subcellular localization revealed that two ERFs and ClAGO5 predominantly localize at the nucleus, suggesting that enhancement of resistance to CGMMV by ETH is probably achieved through ClAGO5 but not ClAGO1. Our findings reveal aspects of the mechanisms underlying RNA silencing in watermelon against CGMMV.     

表油菜素内酯对黄瓜子叶过氧化物酶活性和可溶性蛋白含量的影响

０．５ｍｇ／Ｌ的表油菜素内酯（ｅｐｉ－ＢＲ）能显著地促进黄瓜子叶叶绿素ａ、叶绿素ｂ的含量和叶绿素ａ／叶绿素ｂ比值的下降,表明ｅｎｉ－ＢＲ能促进子叶的衰老。从过氧化物酶（ＰＯＤ）的活性测定及同工酶谱发现ｅｐｉ－ＢＲ可提高其活性,暗示它可能通过提高子叶ＰＯＤ的活性而加速子叶叶绿素的降解。另一方面,ｅｐｉ－ＢＲ促进子时可溶性蛋白含量的下降,其中主要是ＲｕＢＰ羧化酶含量的下降,同时,ｅｐｉ－ＢＲ引起子叶游离氨基酸的累积。