The effects of copper on photosynthesis and biomolecules yield in Chlorolobion braunii.

Our knowledge of the effects of copper on microalgal physiology is largely based on studies conducted with high copper concentrations; much less is known when environmentally relevant copper levels come into question. Here, we evaluated the physiology of Chlorolobion braunii exposed to free copper ion concentrations between 5.7 × 10-9 and 5.0 × 10-6  mol · L-1 , thus including environmentally relevant values. Population growth and maximum photosynthetic quantum yield of PSII were determined daily during the 96 h laboratory controlled experiment. Exponentially-growing cells (48 h) were analyzed for effective quantum yield and rapid light curves (RLC), and total lipids, proteins, carbohydrates, chlorophyll a and carotenoids were determined. The results showed that growth rates and population density decreased gradually as copper increased in experiment, but the photosynthetic parameters (maximum and effective quantum yields) and photochemical quenching (qP) decreased only at the highest free copper concentration tested (5.0 × 10-6 mol · L-1 ); nonphotochemical quenching (NPQ) increased gradually with copper increase. The RLC parameters Ek and rETRmax were inversely proportional to copper concentration, while α and Im decreased only at 5.0 × 10-6 mol · L-1 . The effects of copper in biomolecules yield (mg · L-1 ) varied depending on the biomolecule. Lipid yield increased at free copper concentration as low as 2.5 × 10-8 mol · L-1 , but proteins and carbohydrates were constant throughout.

Cu and Cd affect distinctly the physiology of a cosmopolitan tropical freshwater phytoplankton.

Copper and Cd are natural constituents of freshwater ecosystems, both cycling influenced by microbial communities. The present research examined the impacts of environmentally relevant concentrations of Cu and Cd on the growth, viability, cell size, chlorophyll a (Chl a) content and photochemical efficiency of the tropical freshwater phytoplankton Chlorolobion braunii. Cell growth was significantly impaired by Cu and Cd, with EC50 occurring at 33.6 and 1.6µM, respectively. At sublethal levels (< EC50), cell death was already induced at 5µM Cu and 1µMCd. Average cell volume significantly increased as metal concentrations increased, as did the Chl a content per cell, although the Chl a content per unit volume decreased. Copper did not affect both the photosystem II (PSII) maximum quantum yield (ΦM) or the operational quantum yield (ΦE), while Cd significantly impacted ΦE, with EC50 occurring at 18.4µM. Different responses for Cu and Cd were obtained whether the photochemical fluorescence quenching (Qp) or non-photochemical quenching (Qn) were considered. Qp decreased after Cd addition, but was not altered after Cu addition. Qn values significantly increased after the addition of either metal. Non-photochemical quenching due to heat dissipation (NPQ) significantly increased in response to both metals, but it was more pronounced in the case of Cd. Overall, Cd was more toxic to C. braunii than Cu.

Effect of post-weaning growth rate on carcass traits and meat quality of Nellore cattle.

This study evaluated the effects of growth rate during post-weaning growing phase on carcass traits and beef quality. Thirty-four Nellore young bulls were randomly assigned to one of three treatments: LOW, MEDIUM or HIGH growth rate during post-weaning growing phase followed by high growth rate in the finishing phase. The growth rate affected (P<0.05) all carcass traits evaluated at the end of post-weaning growing phase, except ultimate pH. Carcass dressing was greatest (P<0.05) for the HIGH growth rate group in both phases. Beef from the HIGH group exhibited the greatest (P<0.05) sarcomere length and a* and b* colour values at the end of post-weaning growing phase. However, post-weaning growth rate did not affected (P>0.05) collagen content and solubility, myofibrillar fragmentation index and Warner-Bratzler shear force. Our data suggest that a low post-weaning growth rate produces lighter and leaner carcasses, but it does not affect meat quality traits in Nellore young bulls.

Identification of putative TAL effector targets of the citrus canker pathogens shows functional convergence underlying disease development and defense response.

BACKGROUND: Transcriptional activator-like (TAL) effectors, formerly known as the AvrBs3/PthA protein family, are DNA-binding effectors broadly found in Xanthomonas spp. that transactivate host genes upon injection via the bacterial type three-secretion system. Biologically relevant targets of TAL effectors, i.e. host genes whose induction is vital to establish a compatible interaction, have been reported for xanthomonads that colonize rice and pepper; however, citrus genes modulated by the TAL effectors PthA"s" and PthC"s" of the citrus canker bacteria Xanthomonas citri (Xc) and Xanthomonas aurantifolii pathotype C (XaC), respectively, are poorly characterized. Of particular interest, XaC causes canker disease in its host lemon (Citrus aurantifolia), but triggers a defense response in sweet orange. RESULTS: Based on, 1) the TAL effector-DNA binding code, 2) gene expression data of Xc and XaC-infiltrated sweet orange leaves, and 3) citrus hypocotyls transformed with PthA2, PthA4 or PthC1, we have identified a collection of Citrus sinensis genes potentially targeted by Xc and XaC TAL effectors. Our results suggest that similar with other strains of Xanthomonas TAL effectors, PthA2 and PthA4, and PthC1 to some extent, functionally converge. In particular, towards induction of genes involved in the auxin and gibberellin synthesis and response, cell division, and defense response. We also present evidence indicating that the TAL effectors act as transcriptional repressors and that the best scoring predicted DNA targets of PthA"s" and PthC"s" in citrus promoters predominantly overlap with or localize near to TATA boxes of core promoters, supporting the idea that TAL effectors interact with the host basal transcriptional machinery to recruit the RNA pol II and start transcription. CONCLUSIONS: The identification of PthA"s" and PthC"s" targets, such as the LOB (lateral organ boundary) and CCNBS genes that we report here, is key for the understanding of the canker symptoms development during host susceptibility, or the defenses of sweet orange against the canker bacteria. We have narrowed down candidate targets to a few, which pointed out the host metabolic pathways explored by the pathogens.