Effects of fire on abundance of Eragrostis intermedia in a semi-arid grassland in southeastern Arizona

Abstract. Eragrostis intermedia (Plains lovegrass) is a midheight perennial bunchgrass native to semi-arid grasslands of the southwestern USA, that becomes an abundant and dominant component of these grasslands in areas long protected from livestock grazing. Substantial mortality of plains lovegrass occurred on a large livestock exclosure in southeastern Arizona, after a period of declining precipitation, but only in areas that had not burned in the previous three years. Lovegrass abundance subsequently increased on both undisturbed and burned sites, but remained substantially higher on the burned area. Long-term abundance of plains lovegrass may depend on episodic fire, particularly during periods of reduced precipitation.     

Polygalacturonase-inhibiting protein accumulates in Phaseolus vulgaris L. in response to wounding, elicitors and fungal infection

Polygalacturonase-inhibiting protein (PGIP) is a cell wall-associated protein that specifically binds to and inhibits the activity of fungal endopolygalacturonases. The Phaseolus vulgaris gene encoding PGIP has been cloned and characterized. Using a fragment of the cloned pgip gene as a probe in Northern blot experiments, it is demonstrated that the pgip mRNA accumulates in suspension-cultured bean cells following addition of elicitor-active oligogalacturonides or fungal glucan to the medium. Rabbit polyclonal antibodies specific for PGIP were generated against a synthetic peptide designed from the N-terminal region of PGIP; the antigenicity of the peptide was enhanced by coupling to KLH. Using the antibodies and the cloned pgip gene fragment as probes in Western and Northern blot experiments, respectively, it is shown that the levels of PGIP and its mRNA are increased in P. vulgaris hypocotyls in response to wounding or treatment with salicylic acid. Using gold-labeled goat-anti-rabbit secondary antibodies in EM studies, it has also been demonstrated that, in bean hypocotyls infected with Colletotrichum lindemuthianum, the level of PGIP preferentially increases in those cells immediately surrounding the infection site. The data support the hypothesis that synthesis of PGIP constitutes an active defense mechanism of plants that is elicited by signal molecules known to induce plant defense genes.     

Effects of promoter,intron and enhancer elements on transient gene expression in sugar-cane and carrot protoplasts

Various chimaeric promoter regions coupled to the uidA -glucuronidase gene were evaluated for transient expression strength following electroporation into sugar-cane (monocot) and carrot (dicot) protoplasts. Multiple enhancer elements increased expression in sugar-cane, by up to 400-fold for the artificial Emu promoter relative to the CaMV 35S promoter. The relative expression strengths of promoters varied substantially between the species. Sugar-cane also differed in some respects from previously tested species in the family Poaceae. For example, in sugar-cane the nopaline synthase and CaMV 35S promoters were of equivalent strength, and insertion of Adh1 intron 1 into the 5 transcribed region decreased expression strength.     

Cell wall synthesis during growth and maturation of Nitella internodal cells

An improved ¹³C-density-labeling method was used to study cell wall synthesis in rapidly expanding, slowly expanding and recently mature internodes of Nitella translucens var axillaris (A.Br.) R.D.W. As cells matured, the rate of wall synthesis slowed and the deposition of cellulose microfibrils changed from a predominantly transverse direction in the primary wall of rapidly expanding internodes to a helicoidal array in the secondary wall of mature internodes. The secondary wall was characterized by relatively higher rates of cellulose synthesis and lower rates of pectin synthesis than the primary wall. The synthesis of xyloglucan also decreased markedly at the transition to secondary wall synthesis, while the synthesis of mannose-rich hemicellulose increased. Even though structural differences were striking between the primary and secondary walls of Nitella, compositional differences between the two types of wall were quantitative rather than qualitative. The authors appreciate the assistance of Martin Yousef with the electron microscopy.     

A matter of timing: System requirements for repair and their temporal dimensions

Research into repair within the circular economy (CE) typically focuses on technical aspects of design, policy, and markets, and often assumes simplified conditions for the user/owner and the product system to explain the barriers to scaling repair activities. However, factors occurring at pre-use stages of the product's life cycle can significantly influence whether, and to what extent, repair is viable or possible, that is, warranty duration, after-sale service provision, and access to necessities. The passing of time can directly and indirectly affect the ability, difficulty, and thus, the likelihood of repair activities being performed at each stage of the product's life cycle. Drawing from the literature and applying inductive systems-thinking tools, we propose a framework for considering the “System of Repairability.” We delineate how the passing of time (temporal dimensions) affects one's ‘‘ability to repair,’’ as a product progresses through different life cycle phases (i.e., breakdown vs. repair vs. disposal), and the point(s) at which the repair is considered or attempted (i.e., year of usage). By integrating life cycle and temporal (time-based) dimensions into a broad System of Repairability framework, we clarify relevant interconnections, iterations, sequences, and timing of decision points, stakeholders, and necessary conditions to facilitate an outcome of successful repair at the individual level, and thus intervention strategies for scaling repair within CE. We discuss how a policy mix can address the life cycle of products and the repair system more holistically. We conclude with a future outlook on how temporal dimensions can inform policy strategies and future research.     

Regulated expression of the rat medium chain hydrolase gene in transgenic rape seed

Medium chain hydrolase (MCH) is an enzyme which regulates the chain length of fatty acid synthesis specifically in the mammary gland of the rat. During lactation, MCH interacts with fatty acid synthase (FAS) to cause premature release of acyl chains, thus providing medium chain fatty acids for synthesis of milk fat. In this study we have investigated the ability of rat MCH to interact with the phylogenetically more distant FAS structure present in plant systems and to cause a perturbation of fatty acid synthesis. Inin vitro experiments, addition of purified MCH to rapeseed homogenates was found to cause a significant perturbation of fatty acid synthesis towards medium chain length products. The rat MCH gene was expressed in transgenic oilseed rape using a seed specific rape acyl carrier protein (ACP) promoter and a rape ACP plastid targeting sequence. Western analysis showed MCH protein to be present in transgenic seed and for its expression to be developmentally regulated in concert with storage lipid synthesis. The chimaeric preprotein was correctly processed and immunogold labelling studies confirmed MCH to be localized within plastid organelles. However, fatty acid analysis of oil from MCH-expressing rape seed showed no significant differences to that from control seed.