pH effects on the lipid and fatty acids accumulation in Chlamydomonas reinhardtii.

pH variations influence the delivery of essential nutrients and CO2 solubility, which impact algae metabolism. In this study the microalgal growth and chlorophyll, lipid, and fatty acids content; along with the expression of some genes implicated in the biosynthesis of lipids were examined in Chlamydomonas reinhardtii subjected to pH values of 7.0, 7.8, and 8.5. At pH 7.8 an increase in cell growth was observed with a significant accumulation of chlorophyll (1.75-fold) when compared with growth at pH 7, while at pH 8.5 a sharp decrease in both parameters was observed when compared with the other pH values tested. Lipid content increased 3.0 (14.81% of dry cell weight, dcw) and 2.3 times (11.43% dcw) at pH 7.8 and 8.5, respectively, when compared with the experiment at pH 7 (4.97% dcw). The compositions of major fatty acids in the strains growing at pH 7.0, 7.8, or 8.5 were 25.7, 28.0, and 32.1% for palmitic acid; 17.3, 14.7, and 25.7% for oleic acid; and 9.8, 12.1, and 4.6% for linoleic acid; respectively. qRT-PCR analysis showed that the transcripts of ß-carboxyltransferase, Acyl carrier protein 1, acyl-ACP thiolase 1, acyl-sn-glycerol-3-phosphate acyltransferase, and diacylglycerol acyl transferase isoform 3 were significantly induced at pH 7.8 when compared with the other two pH conditions. These results indicate that the induction of genes implicated in the early and final steps of lipid biosynthesis contributes to their accumulation in the stationary phase. Our research suggests that a pH of 7.8 might be ideal to maximize growth and lipid accumulation.

Pregnancy and Litter Size, But Not Lamb Sex, Affect Feed Intake and Wool Production by Merino-Type Ewes.

Two experiments (Australia and Mexico) tested whether feed intake (FI) and wool production (WP) are affected by pregnancy (PRG), litter size (LZ), or lamb sex (LS) in Merino-type ewes. In Experiment-1, ewes were either not pregnant (NPR; n = 6), or carrying 1 (PR1; n = 7) or 3 (PR3; n = 11) fetuses, were studied in individual pens. NPR ewes had lower (p < 0.02) FI throughout PRG and lactation (LAC), except around lambing (p < 0.001). Following lambing, FI increased in PRG ewes (p < 0.001) to double the values in NPR ewes. PRG reduced WP (p < 0.001); in PR3, WP was lower than for both PR1 and NPR (p < 0.001). WP decreased during LAC and was lower in ewes rearing lambs than in NPR ewes (p < 0.001). Experiment-2 used 48 pregnant ewes (28 bearing singles and 20 bearing twins). Dam and lamb live weights (LW) and body condition (BC) were recorded from birth to weaning at 60 d, and dam fleece weight (DFW) was measured at weaning (12 months growth). WP was higher in ewes bearing and rearing single lambs than in ewes bearing twins (p < 0.001). DFW was positively (p < 0.01) related to LZ, dam LW, and BC, but not to changes in dam LW during LAC, or to lamb weight at birth or weaning, or LW gain, or LS. In conclusion, FI was affected during PRG and by LZ during LAC, whereas WP was influenced by LZ, but not LS, only during pregnancy.

Salt stress increases the expression of p5cs gene and induces proline accumulation in cactus pear.

Proline (Pro) is one of the most accumulated osmolytes in salinity and water deficit conditions in plants. In the present study, we measured the Pro content, the activity and the expression level of delta 1-pyrroline-5-carboxylate synthetase (P5CS: gamma-glutamyl kinase, EC 2.7.2.11 and glutamate-5-semialdehyde dehydrogenase, EC 1.2.1.41), a key regulatory enzyme involved in the biosynthesis of Pro, in cactus pear (Opuntia streptacantha) subjected to 6, 9 and 11 days of salt stress. Treatment with NaCl of O. streptacantha young plants resulted in a decrease in the cladode thickness and root length, and in a significant and gradual accumulation of Pro in young cladodes, in a time- and concentration-dependent manner. P5CS activity, studied as gamma-glutamyl kinase, was reduced at all times as a consequence of salt treatment, except at the sixth day at 75 and 150mM of NaCl, where a slight increase was observed. We isolated an open reading frame (ORF) fragment of p5cs gene. The deduced amino acid sequence of the P5CS protein exhibited 90.4% of identity with the P5CS protein from Mesembryanthemum crystallinum. RT-PCR analysis revealed that the Osp5cs gene of O. streptacantha was induced by salt stress at 9 and 11 days of treatment. Furthermore, ABA-induced Osp5cs gene expression was observed in cladodes of cactus pear young plants. We observed an evident correlation between the transcript up-regulation and the Pro accumulation under salt stress; however, these results do not parallel with the changes in P5CS enzymatic activity. This Pro accumulation might function as an osmolyte for the intracellular osmotic adjustment and might be playing a critical role in protecting photosynthetic activity in O. streptacantha plants under salt stress.