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Heterologous expression of the NAD + -dependent phosphite dehydrogenase (PTXD) bacterial enzyme from Pseudomonas stutzerii enables selective growth of transgenic organisms by using phosphite as sole phosphorous source. Combining phosphite fertilization with nuclear expression of the ptxD transgene was shown to be an alternative to herbicides in controlling weeds and contamination of algal cultures. Chloroplast expression of ptxD in Chlamydomonas reinhardtii was proposed as an environmentally friendly alternative to antibiotic resistance genes for plastid transformation. However, PTXD activity in the chloroplast is low, possibly due to the low NAD + /NADP + ratio, limiting the efficiency of phosphite assimilation. We addressed the intrinsic constraints of the PTXD activity in the chloroplast and improved its catalytic efficiency in vivo via rational mutagenesis of key residues involved in cofactor binding. Transplastomic lines carrying a mutagenized PTXD version promiscuously used NADP + and NAD + for converting phosphite into phosphate and grew faster compared to those expressing the wild type protein. The modified PTXD enzyme also enabled faster and reproducible selection of transplastomic colonies by directly plating on phosphite-containing medium. These results allow using phosphite as selective agent for chloroplast transformation and for controlling biological contaminants when expressing heterologous proteins in algal chloroplasts, without compromising on culture performance., Competing Interests: The authors declare no conflicts of interest

Reversible phosphorylation of thylakoid proteins contributes to photoacclimation responses in photosynthetic organisms, enabling the fine-tuning of light harvesting under changing light conditions and promoting the onset of photoprotective processes. However, the precise functional role of many of the described phosphorylation events on thylakoid proteins remains elusive. The calcium sensor receptor protein (CAS) has previously been indicated as one of the targets of the state transition kinase 8 (STN8). Here we show that in Arabidopsis thaliana , CAS is also phosphorylated by the state transition kinase 7 (STN7), as well as by another, so-far unknown, Ca 2+ -dependent kinase. Phosphoproteomics analysis and in vitro phosphorylation assays on CAS variants identified the phylogenetically conserved residues Thr-376, Ser-378, and Thr-380 as the major phosphorylation sites of the STN kinases. Spectroscopic analyses of chlorophyll fluorescence emission at 77K further showed that, while the cas mutant is not affected in state transition, it displays a persistent strong excitation of PSI under high light exposure, similar to the phenotype previously observed in other mutants defective in photoacclimation mechanisms. Together with the observation of a strong concomitant phosphorylation of light harvesting complex II (LHCII) and photosynthetic core proteins under high irradiance in the cas mutant this suggests a role for CAS in the STN7/STN8/TAP38 network of phosphorylation-mediated photoacclimation processes in Arabidopsis.

An 80-year-old man presented with subjective fever, chronic cough occasionally producing scant yellow sputum, retrosternal pleuritic pain, and dyspnea on walking one block. Since symptom onset three months earlier, he had lost 20 pounds; he had had two loose stools a day, fatigue, malaise, and anorexia but not hemoptysis, nausea, vomiting, hematemesis, hematochezia, or melena. He denied paroxysmal nocturnal dyspnea or orthopnea. As far as could be ascertained, he not recently been exposed to tuberculosis or any other infectious disease. He had previously been seen at another clinic and had completed a 10-day trial of erythromycin (500 mg p.o. q12 h) without apparent change in symptoms.

A 58-year-old man presented with profuse diarrhea, abdominal distention, flatulence, weakness, and a 15-lb weight loss. The initial symptoms of nausea and vomiting had begun a week earlier, within hours of eating chicken that had not been well wrapped when purchased. Two days after symptom onset, he received intravenous rehydration therapy at another hospital. With resolution of the nausea and vomiting, he felt slightly better and went home against medical advice. He had not had fever, chills, hematochezia, melena, hematemesis, or dysuria.

A 40-year-old man presented with a three-week history of malaise, nausea, night sweats, decreased appetite, and a 15-lb weight loss. He reported having had diarrhea, occasionally with bright red blood, for the first two weeks and a temperature as high as 39.4 degrees C for the last two weeks. He had not had cough, shortness of breath, wheezing, chest pain, arthralgias, rash, or conjunctivitis. He had not eaten raw oysters or raspberries.