We combined transcriptomic and biochemical approaches to study rhizobial and plant sulfur (S) metabolism in nitrogen (N) fixing nodules (Fix + ) of Lotus japonicus, as well as the link of S-metabolism to symbiotic nitrogen fixation and the effect of nodules on whole-plant S-partitioning and metabolism. Our data reveal that N-fixing nodules are thiol-rich organs. Their high adenosine 59-phosphosulfate reductase activity and strong 35 S-flux into cysteine and its metabolites, in combination with the transcriptional upregulation of several rhizobial and plant genes involved in S-assimilation, highlight the function of nodules as an important site of S-assimilation. The higher thiol content observed in nonsymbiotic organs of N-fixing plants in comparison to uninoculated plants could not be attributed to local biosynthesis, indicating that nodules are an important source of reduced S for the plant, which triggers whole-plant reprogramming of S-metabolism. Enhanced thiol biosynthesis in nodules and their impact on the whole-plant S-economy are dampened in plants nodulated by Fix 2 mutant rhizobia, which in most respects metabolically resemble uninoculated plants, indicating a strong interdependency between N-fixation and S-assimilation.

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Milk protein synthesis in the mammary gland involves expression of six major milk proteins' genes whose nutritional regulation remains poorly defined. In this study, the effect of long-term under- and overfeeding on the expression of as1-casein: CSN1S1, as2-casein: CSN1S2, β-casein: CSN2, κ-casein: CSN3, α-lactalbumin: LALBA and β-lactoglobulin: BLG gene in goat mammary tissue (MT) was examined. Twenty-four lactating dairy goat, at 90-98 days in milk, were divided into three homogenous subgroups and fed the same ration, for 60 days, in quantities which met 70% (underfeeding), 100% (control) and 130% (overfeeding) of their energy and crude protein requirements. The results showed a significant decrease in mRNA of CSN1S2, CSN2, CSN3 and LALBA genes in the MT of underfed goats compared with the overfed and on the CSN1S1 and BLG gene expressions in the MT of underfed goats compared with the respective control and overfed. CSN2 was the most abundant transcript in goat MT relative to the other milk proteins' genes. Significantly positive correlations were observed between the mRNA levels of caseins' and BLG genes with the milk yield. Moreover, a significant correlation was found between the mRNA levels of CSN1S2 with the milk protein, lactose content and lactose yield and also between the LALBA gene expression with the lactose content and lactose yield respectively. In conclusion, the feeding level and consequently the nutrients availability affected the milk lactose content, protein and lactose yield as well as the milk volume by altering the CSN1S1, CSN1S2, CSN2, CSN3, LALBA and BLG gene expression involved in their metabolic pathways.