Nitrogen starvation-induced accumulation of triacylglycerol in the green algae: evidence for a role for ROC40, a transcription factor involved in circadian rhythm.

Microalgal triacylglycerol (TAG), a promising source of biofuel, is induced upon nitrogen starvation (-N), but the proteins and genes involved in this process are poorly known. We performed isobaric tagging for relative and absolute quantification (iTRAQ)-based quantitative proteomics to identify Chlorella proteins with modulated expression under short-term -N. Out of 1736 soluble proteins and 2187 membrane-associated proteins identified, 288 and 56, respectively, were differentially expressed under -N. Gene expression analysis on select genes confirmed the same direction of mRNA modulation for most proteins. The MYB-related transcription factor ROC40 was the most induced protein, with a 9.6-fold increase upon -N. In a previously generated Chlamydomonas mutant, gravimetric measurements of crude total lipids revealed that roc40 was impaired in its ability to increase the accumulation of TAG upon -N, and this phenotype was complemented when wild-type Roc40 was expressed. Results from radiotracer experiments were consistent with the roc40 mutant being comparable to the wild type in recycling membrane lipids to TAG but being impaired in additional de novo synthesis of TAG during -N stress. In this study we provide evidence to support the hypothesis that transcription factor ROC40 has a role in -N-induced lipid accumulation, and uncover multiple previously unknown proteins modulated by short-term -N in green algae.

Metabolic regulation of triacylglycerol accumulation in the green algae: identification of potential targets for engineering to improve oil yield.

The great need for more sustainable alternatives to fossil fuels has increased our research interests in algal biofuels. Microalgal cells, characterized by high photosynthetic efficiency and rapid cell division, are an excellent source of neutral lipids as potential fuel stocks. Various stress factors, especially nutrient-starvation conditions, induce an increased formation of lipid bodies filled with triacylglycerol in these cells. Here we review our knowledge base on glycerolipid synthesis in the green algae with an emphasis on recent studies on carbon flux, redistribution of lipids under nutrient-limiting conditions and its regulation. We discuss the contributions and limitations of classical and novel approaches used to elucidate the algal triacylglycerol biosynthetic pathway and its regulatory network in green algae. Also discussed are gaps in knowledge and suggestions for much needed research both on the biology of triacylglycerol accumulation and possible avenues to engineer improved algal strains.

Conversion of membrane lipid acyl groups to triacylglycerol and formation of lipid bodies upon nitrogen starvation in biofuel green algae Chlorella UTEX29.

Algal lipids are ideal biofuel sources. Our objective was to determine the contributors to triacylglycerol (TAG) accumulation and lipid body formation in Chlorella UTEX29 under nitrogen (N) deprivation. A fivefold increase in intracellular lipids following N starvation for 24 h confirmed the oleaginous characteristics of UTEX29. Ultrastructural studies revealed increased number of lipid bodies and decreased starch granules in N-starved cells compared to N-replete cells. Lipid bodies were observed as early as 3 h after N removal and plastids collapsed after 48 h of stress. Moreover, the identification of intracellular pyrenoids and differences in the expected nutritional requirements for Chlorella protothecoides (as UTEX29 is currently classified) led us to conduct a phylogenetic study using 18S and actin cDNA sequences. This indicated UTEX29 to be more phylogenetically related to Chlorella vulgaris. To investigate the fate of different lipids after N starvation, radiolabeling using ¹4C-acetate was used. A significant decrease in ¹4C-galactolipids and phospholipids matched the increase in ¹4C-TAG starting at 3 h of N starvation, consistent with acyl groups from structural lipids as sources for TAG under N starvation. These results have important implications for the identification of key steps controlling oil accumulation in N-starved biofuel algae and demonstrate membrane recycling during lipid body formation.

Portuguese Football Federation consensus statement 2020: nutrition and performance in football.

Nutrition is an undeniable part of promoting health and performance among football (soccer) players. Nevertheless, nutritional strategies adopted in elite football can vary significantly depending on culture, habit and practical constraints and might not always be supported by scientific evidence. Therefore, a group of 28 Portuguese experts on sports nutrition, sports science and sports medicine sought to discuss current practices in the elite football landscape and review the existing evidence on nutritional strategies to be applied when supporting football players. Starting from understanding football's physical and physiological demands, five different moments were identified: preparing to play, match-day, recovery after matches, between matches and during injury or rehabilitation periods. When applicable, specificities of nutritional support to young athletes and female players were also addressed. The result is a set of practical recommendations that gathered consensus among involved experts, highlighting carbohydrates periodisation, hydration and conscious use of dietary supplements.

Morpho-anatomical and growth alterations induced by arsenic in Cajanus cajan (L.) DC (Fabaceae).

Arsenic (As) is a toxic element to most organisms. Studies investigating anatomic alterations due to As exposure in plants are scarce but of utmost importance to the establishment of environmental biomonitoring techniques. So, this study aimed to investigate the effects of As on the development and initial root growth in Cajanus cajan (Fabaceae), characterize and quantify the possible damages, evaluate genotoxic effects, and identify structural markers to be used in environmental bioindication. Plants were exposed hydroponically to 0.5, 1.0, 1.5, and 2.0 mg As L(-1), as sodium arsenate. Growth parameters were measured, and in the end of the exposure, root samples were analyzed for qualitative and quantitative anatomical alterations. Arsenic genotoxicity was evaluated through analysis of the mitotic index in the root apex. Compared to the control, As-treated seedlings showed an altered architecture, with significantly decreased root length (due to the lower mitotic index in the apical meristem and reduced elongation of parenchyma cells) with darkened color, and abnormal development of the root cap. A significant increase in vascular cylinder/root diameter ratio was also detected, due to the reduction of the cellular spaces in the cortex. The secondary xylem vessel elements were reduced in diameter and had sinuous walls. The severest damage was visible in the ramification zone, where uncommon division planes of phellogen and cambium cells and disintegration of the parenchyma cells adjacent to lateral roots were observed. The high sensibility of C. cajan to As was confirmed, since it caused severe damages in root growth and anatomy. The main structural markers for As toxicity were the altered root architecture, with the reduction of the elongation zone and increase of ramification zone length, and the root primordia retained within the cortex. Our results show a new approach about As toxicity and indicate that C. cajan is a promising species to be used for bioindication of environmental contamination by As.