Characterization, tissue distribution of apela and periprandial, fasting and refeeding changes of apela mRNA in Siberian sturgeon Acipenser baerii.

Apela identified from zebrafish Danio rerio for the first time in 2013 is a novel endogenous peptide ligand for the apelin receptor. To study the role of apela in regulating fish feeding, the complementary (c) DNA sequence of apela of Siberian sturgeon Acipenser baerii was cloned for the first time. The apela cDNA fragment of 836 bp was obtained by cloning. The open reading frame (ORF) of apela was 165 bp encoding a 54 amino acid, including 22 amino acids signal peptide and two proteolytic sites. Phylogenetic tree analysis showed that A. baerii apela was clustered with mammalian and amphibian sequences. A. baerii apela messeger (m)RNA was widely distributed in 11 tissues related to feeding, with high expressions in brain, oesophagus and stomach, especially in the brain. The level of apela mRNA in brain increased significantly after feeding. On the first day of fasting, apela expression in brain was significantly lower than that of the fed group, but after fasting for 3-15 days, the expression of apela in A. baerii brain was significantly higher than that in the fed group. After refeeding apela mRNA expression was obviously reduced. These results suggest that apela plays a bidirectional role in feeding regulation of A. baerii, which may serve as a short-term satiation factor and a long-term hunger factor.

Physicochemical properties of starches and expression and activity of starch biosynthesis-related genes in sweet potatoes.

The functional properties of starches from six sweet potato varieties containing various starch components and structures were studied in an attempt to identify starch sources for industrial uses. Tainan 18 (TNN18) with high-amylose (AM) starch exhibited high setback and breakdown viscosities, high water solubility at 85°C but low swelling volume at 65°C, and high hardness and adhesiveness; in contrast, the low-AM starch of Tainung 31 (TNG31) had opposite characteristics. Seven genes related to starch biosynthesis were tested, and GBSS, SS, SBEII, ISA, and AGPase were highly expressed in TNN18 and TNG31; however, transcript levels in DBE and SBE were extremely low. GBSS and SS activity reflected the abundance of GBSS and SS mRNA in TNG31 and TNN18, and expression of AGPase, GBSS, SS, and SBE in TNN18 substantially increased content of AM. The expression and activity of DBE had a significant effect on TNG31 with increased AP content.