Photosynthesis, photorespiration and nitrogen metabolism

Abstract. The ATP and reduced ferredoxin generated in photosynthetic reactions in the chloroplast are utilized for a large number of reactions other than CO₂-fixation. Quantitatively the most important reaction is the reassimilation of ammonia liberated during photorespiration in C₃ plants via the glutamate synthase cycle. Chloroplasts are also able to reduce nitrite to ammonia, sulphate to sulphide, and synthesize a number of amino acids. The amino acids essential for human nutrition are all synthesized in the chloroplast and evidence is presented to suggest that they may be the sole site of such biosynthetic reactions.     

An Ultrastructural Study of Ingestion and Digestion in Tetrahymena pyriformis*

SYNOPSIS. When the structures involved in digestive events in T. pyriformis are examined at the electron microscope level, some information is added to that long known from light microscopy. The food trapping mechanism consists of the three membranelles, undulating membrane, oral ribs, and a “valve” apparently closing the opening to the cytopharynx. Both of the latter structures are supported by microtubules. Fibers extend internally from the cytopharynx and are closely associated with the food vacuole as it forms. Clear vacuoles resembling pinocytic vacuoles appear to arise from differentiated areas of the pellicle and plasma membrane. These vacuoles may fuse with primary lysosomes. Hydrolases are thus contributed to the pinocytic vacuoles which may then fuse with food vacuoles. When first formed food vacuoles contain no hydrolases but may acquire them directly, from primary lysosomes or from pinocytic vacuoles. Digestion proceeds to completion in the food vacuole, at which time soluble food products are released to the cytoplasm. Undigested materials are lost through the cytopyge. In stationary growth phase cells autophagic vacuoles form containing mitochondria and other cellular particulates. Such vacuoles probably contain hydrolases when formed and they may receive others by fusion with primary lysosomes.     

The Gamete-Shedding Substances of Starfishes: A Physiological-Biochemical Study

A shedding substance, found in the radial nerves of 14 speciesof starfish, induced the release of gametes from intact animalsas well as from whole or fragmented gonads. The shedding substancewas not sex-specific, being present in the radial nerves ofboth males and females throughout the year, and, in general,was not species-specific. This neurosecretory-like polypeptideappeared to function by stimulating ovarian muscle to contract,and was calcium-dependent: it also stimulated the maturationof immature eggs. The shedding substance has been purified andits amino acid composition investigated. A second physiologically-active material, termed "shedhibin"because it inhibited shedding activity, was also found in theradial nerves of ripe sea stars. In the presence of shedhibin,normally-adequate quantities of shedding substance would notcause the release of gametes from isolated ovarian fragments.It appeared that although the level of shedding substance wasconstant throughout the year, the level of shedhibin fluctuated,possibly controlling the natural release of gametes from seastars. The precise chemical nature of shedhibin has yet to bedetermined.     

Closed loop bioreactor system for the ex vivo expansion of human T cells

Background aim

Translation of therapeutic cell therapies to clinical-scale products is critical to realizing widespread success. Currently, however, there are limited tools that are accessible at the research level and readily scalable to clinical-scale needs.

Mapping of quantitative trait loci for oil content in cottonseed kernel

Oil content in cottonseed is a major quality trait which when improved through breeding could enhance the competitiveness of cottonseed oil among other vegetable oils. Cottonseed oil content is a quantitative trait controlled by genes in the tetraploid embryo and tetraploid maternal plant genomes, and the knowledge of quantitative trait loci (QTLs) and the genetic effects related to oil content in both genomes could facilitate the improvement in its quality and quantity. However, till date, QTL mapping and genetic analysis related to this trait in cotton have only been conducted in the tetraploid embryo genome. In the current experiment, an IF₂ population of cottonseed kernels from the random crossing of 188 intraspecific recombinant inbred lines which were derived from the hybrid of two parents, HS46 and MARCABUCAG8US-1-88, were used to simultaneously locate QTLs for oil content in the embryo and maternal plant genomes. The four QTLs found to be associated with oil content in cottonseed were: qOC-18-1 on chromosome 18; qOC-LG-11 on linkage group 11; qOC-18-2 on chromosome 18; and qOC-22 on chromosome 22. At a high selection threshold of 0.05, there was strong evidence linking the QTLs above the oil content in cottonseed. Embryo additive and dominant effects from the tetraploid embryo genome, as well as maternal additive effects from the tetraploid maternal plant genome were found to be significant contributors to genetic variation in cottonseed oil content.     

Systematics of the Platyrrhinus helleri species complex (Chiroptera: Phyllostomidae), with descriptions of two new species

Platyrrhinus is a diverse genus of small to large phyllostomid bats characterized by a comparatively narrow uropatagium thickly fringed with hair, a white dorsal stripe, comparatively large inner upper incisors that are convergent at the tips, and three upper and three lower molars. Eighteen species are currently recognized, the majority occurring in the Andes. Molecular, morphological, and morphometric analyses of specimens formerly identified as Platyrrhinus helleri support recognition of Platyrrhinus incarum as a separate species and reveal the presence of two species from western and northern South America that we describe herein as new ( Platyrrhinus angustirostris sp. nov. from eastern Colombia and Ecuador, north‐eastern Peru, and Venezuela and Platyrrhinus fusciventris sp. nov. from Guyana, Suriname, French Guiana, Trinidad and Tobago, northern Brazil, eastern Ecuador, and southern Venezuela). These two new species are sister taxa and, in turn, sister to Platyrrhinus incarum. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 785–812.     

Cold-induced repression of the rice anther-specific cell wall invertase gene OSINV4 is correlated with sucrose accumulation and pollen sterility

Low temperatures during rice (Oryza sativa L.) pollen development cause pollen sterility and decreased grain yield. We show that the time of highest sensitivity to cold coincides with the time of peak tapetal activity: the transition of the tetrad to early uni-nucleate stage (young microspore, YM stage). Low temperatures at this stage of pollen development result in an accumulation of sucrose in the anthers, accompanied by decreased activity of cell wall bound acid invertase and depletion of starch in mature pollen grains. Expression analysis of two cell wall (OSINV1, 4) and one vacuolar (OSINV2) acid invertase genes showed that OSINV4 is anther-specific and down-regulated by cold treatment. OSINV4 is transiently expressed in the tapetum cell layer at the YM stage, and later from the early binucleate stage in the maturing microspores. The down-regulation of OSINV4 expression in the tapetum at YM may cause a disruption in hexose production and starch formation in the pollen grains. In a cold-tolerant cultivar, OSINV4 expression was not reduced by cold; sucrose did not accumulate in the anthers and starch formation in the pollen grains was not affected.