Salt-induced expression of intracellular vesicle trafficking genes, CaRab-GTP, and their association with Na(+) accumulation in leaves of chickpea (Cicer arietinum L.)

Background: Chickpea is an important legume and is moderately tolerant to salinity stress during the growing season. However, the level and mechanisms for salinity tolerance can vary among accessions and cultivars. A large family of CaRab-GTP genes, previously identified in chickpea, is homologous to intracellular vesicle trafficking superfamily genes that play essential roles in response to salinity stress in plants. Results: To determine which of the gene family members are involved in the chickpea salt response, plants from six selected chickpea accessions (Genesis 836, Hattrick, ICC12726, Rupali, Slasher and Yubileiny) were exposed to salinity stress and expression profiles resolved for the major CaRab-GTP gene clades after 5, 9 and 15 days of salt exposure. Gene clade expression profiles (using degenerate primers targeting all members of each clade) were tested for their relationship to salinity tolerance measures, namely plant biomass and Na+ accumulation. Transcripts representing 11 out of the 13 CaRab clades could be detected by RT-PCR, but only six (CaRabA2, -B, -C, -D, -E and -H) could be quantified using qRT-PCR due to low expression levels or poor amplification efficiency of the degenerate primers for clades containing several gene members. Expression profiles of three gene clades, CaRabB, -D and -E, were very similar across all six chickpea accessions, showing a strongly coordinated network. Salt-induced enhancement of CaRabA2 expression at 15 days showed a very strong positive correlation (R2 = 0.905) with Na+ accumulation in leaves. However, salinity tolerance estimated as relative plant biomass production compared to controls, did not correlate with Na+ accumulation in leaves, nor with expression profiles of any of the investigated CaRab-GTP genes. Conclusion: A coordinated network of CaRab-GTP genes, which are likely involved in intracellular trafficking, are important for the salinity stress response of chickpea plants.Crystal Sweetman, Gulmira Khassanova, Troy K. Miller, Nicholas J. Booth, Akhylbek Kurishbayev, Satyvaldy Jatayev, Narendra K. Gupta, Peter Langridge, Colin L.D. Jenkins, Kathleen L. Soole, David A. Day and Yuri Shavruko

The enzymes in C4 photosynthesis

[Extract] The history of the resolution of C4 photosynthesis follows a pattern of demonstrating the operation of unique photosynthetic biochemistry by various means and then identifying the enzymes necessary to support that biochemistry. Critical to the developing understanding of this process was the recognition of two types of photosynthetic cells in C4 plants (mesophyll and bundle sheath) with quite different enzyme complements and distinct biochemical roles (see Fig. 3.1). As currently interpreted (see Edwards and Walker, 1983; Hatch, 1987) the reactions unique to the C4 pathway serve, in association with some remarkable modifications of leaf anatomy and ultrastructure, to concentrate CO2 in bundle sheath cells for utilisatiqn by the photosynthetic carbon reduction cycle carboxylase, ribulose L5-bisphosphate carboxylase-oxygenase (Rubisco). The Rubisco-mediated oxygenase reaction and associated photorespiration\ud are thereby eliminated

Biosynthesis and cellular functions of tartaric acid in grapevines

Tartaric acid (TA) is an obscure end point to the catabolism of ascorbic acid (Asc). Here, it is proposed as a “specialized primary metabolite”, originating from carbohydrate metabolism but with restricted distribution within the plant kingdom and lack of known function in primary metabolic pathways. Grapes fall into the list of high TA-accumulators, with biosynthesis occurring in both leaf and berry. Very little is known of the TA biosynthetic pathway enzymes in any plant species, although recently some progress has been made in this space. New technologies in grapevine research such as the development of global co-expression network analysis tools and genome-wide association studies, should enable more rapid progress. There is also a lack of information regarding roles for this organic acid in plant metabolism. Therefore this review aims to briefly summarize current knowledge about the key intermediates and enzymes of TA biosynthesis in grapes and the regulation of its precursor, ascorbate, followed by speculative discussion around the potential roles of TA based on current knowledge of Asc metabolism, TA biosynthetic enzymes and other aspects of fruit metabolism

Diel feeding chronology of the skate raja Agassizii (Müller & Henle) (Pisces, Elasmobranchii) on the continental shelf off Ubatuba, Southeastern Brazil

The diet and diel feeding pattern of the skate Raja agassizii were investigated through analysis of stomach contents. A total of 280 stomachs were collected by a series of hauls during a daily cycle in three periods, 8-10 January 1987, 22-24 July and 2-4 December 1988, from the inner continental shelf of the coastal ecosystem of Ubatuba, São Paulo State, Brazil (25º35'S; 45º00'W). According to the results of the stomach fullness and of the number of fresh prey, it is suggested that this species presents continuity in the feeding activity during a day. The stomach contents were mainly composed of crustaceans. Nematodes, polychaetes and fishes also occurred. No changes were observed in dietary composition between day and night