Soil salinity affects the expression of serine/arginine-rich (SR) genes and isoforms by alternative splicing, which in turn regulates the adaptation of plants to stress.  We previously identified the cassava spliceosomal component 35 like (SCL) and SR subfamilies, belonging to the SR protein family, which are extensively involved in responses to abiotic stresses.  However, the post-transcriptional regulatory mechanism of cassava arginine/serine-rich (RS) subfamily in response to salt stress remains to be explored.  In the current study, we identified 37 genes of the RS subfamily from 11 plant species and systematically investigated the transcript levels of the RS40 and RS31 genes under diverse abiotic stress conditions.  Subsequently, an analysis of the conserved protein domains revealed that plant RS subfamily genes were likely to preserve their conserved molecular functions and played critical functional roles in responses to abiotic stresses.  Importantly, we found that overexpression of MeRS40 in Arabidopsis enhanced salt tolerance by maintaining reactive oxygen species homeostasis and up-regulating the salt-responsive genes.  However, overexpression of MeRS40 gene in cassava reduced salt tolerance due to the depression of its endogenous gene expression by negative autoregulation of its own pre-mRNA.  Moreover, the MeRS40 protein interacted with MeU1-70Ks (MeU1-70Ka and MeU1-70Kb) in vivo and in vitro, respectively.  Therefore, our findings highlight the critical role of cassava SR proteins in responses to salt stress in plants. 

Ovine bones are the major by-products after slaughtered.  The present study was conducted to extract and characterize acid soluble collagens (ASC) and pepsin soluble collagens (PSC) from ovine bones (Ujumuqin sheep).  Ovine bones collagen were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) as type I collagen.  The results of Fourier transform infrared (FTIR) spectra analysis testified the existence of triple superhelical structure in both ASC and PSC, showing pepsin did not disrupt the triple helical structure of ovine bones collagen.  Glycine, accounting for one-third of total amino acids, was the major amino acid for ovine bones collagen.  Higher imino acid content was responsible for higher thermal denaturation temperature of ovine bones collagen compared to fish collagens.  The isoelectric point of ASC was lower than PSC due to the higher content of acidic amino acids.  Therefore, this study provides the potential reference for collagen extraction and application of ovine bones by-procduct.

In two experiments, the effects of succinate and NADH (reduced nicotinamide adenine dinucleotide) on metmyoglobin reductase activity and electron transport chain-linked metmyoglobin reduction were investigated and compared. In experiment 1, metmyoglobin (MetMb), substrate and inhibitors were incubated with mitochondria. Comparsion of the effects of succinate and NADH on MetMb reduction was investigated. The MetMb percentage in sample treated with 8 mol L-1 succinate decreased by about 69% after 3 h incubation, and the effect was inhibited by the addition of 10 mol L-1 electron transfer chain complex II inhibitor malonic acid; the MetMb percentage in samples treated with 2 mol L-1 NADH decreased by 56% and the effect was inhibited by the addition of 0.02 mol L-1 electron transport chain complex I inhibitor rotenone. These results indicated that electron transport chain played an important role in MetMb reduction. Both complex II and complex I take part in the MetMb reduction in mitochondria through different pathways. NADH-MetMb reduction system was less stable than succinate- MetMb system. In experiment 2, the beef longissimus dorsi muscle was blended with different concentrations of succinate or NADH. Enhancing patties with higher concentration of succinate or NADH improved colour stability in vacuum packaged samples (P<0.05). These results verified that mitochondria electron transport chain is related to the MetMb reduction in meat system.

Fatty acid composition of neutral lipids (NLs), phospholipids (PLs) and free fatty acids (FFAs) from intramuscular fat (IMF), lipid oxidation and lipase activity in muscle Semimembranosus (SM) and msucle Biceps femoris (BF) of dry-cured Xuanwei ham during the 90-d salting stages were analysed. The salt content increased from 0.34 to 3.52% in BF and from 0.10 to 5.42% in SM during the 90 d salting stage, respectively. PLs of IMF in both BF and SM decreased 54.70% (P<0.001) and 34.64% (P<0.05), furthermore, the saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) of PLs in both muscles were hydrolysed almost isochronously. FFAs were increased from 0.46 g 100 g-1 lipids to 2.92 g 100 g-1 lipids in BF at the end of salting, which was lower than SM (from 1.29 g 100 g-1 lipids to 9.70 g 100 g-1 lipids). The activities of acid lipase, neutral lipase and acid phospholipase all remained active in the 90 d. The thiobarbituric acid reactive substances (TBARS) was slowly increased to 1.34 mg kg-1 muscle in BF and to 2.44 mg kg-1 muscle in SM during the salting stage. In conclusion, the controlled salting process prompted the hydrolysis of PLs of IMF notably and increased the lipid oxidation of muscles within some limits.