Effects of porcine somatotropin administration on the responses to dietary lysine and a near-ideal blend of amino acids on the amino acid composition of whole-body protein and amino acid accretion rate in growing pigs.

An experiment was conducted to assess the effects of porcine somatotropin (pST) on the responses to a near-ideal blend of AA on the AA composition of empty, whole-empty body (WEB) protein and WEB essential AA accretion rate in pigs from 22 to 60 kg BW. Forty Hampshire × Yorkshire gilts were individually penned and assigned to a 4 × 2 factorial arrangement of treatments consisting of four diets with and without pST injection. A fortified corn-soybean meal basal diet was formulated to contain 1.50% total Lys with Thr, Met, and Trp added to obtain a near-ideal blend of these AA relative to Lys. In three additional diets, Lys was reduced to 1.25%, 1.00%, and 0.75% by diluting the basal diet with cornstarch, cellulose, and sand such that the diets also contained the same ratios of AA. Pigs that received pST were administered a daily i.m. injection of 2 mg of pST. At 60 kg BW, the WEB (carcass, head, viscera, blood, nails, and hair) was ground and analyzed for proximate and AA composition. Administration of pST increased (P < 0.001) accretion rates of WEB protein and essential AA. Increasing dietary essential AA increased (quadratic, P < 0.03) accretion rate of WEB protein, His, Leu, Trp, and Val in pST-treated pigs, but not in untreated pigs. Lysine composition in the accreted WEB protein was not affected (P > 0.05) by dietary Lys. The efficiency of Lys utilization for WEB Lys accretion was linearly affected (P < 0.01) by dietary Lys. These results indicated that the dietary Lys needed to achieve maximum WEB Lys accretion is markedly increased by pST administration.

This study evaluated the effects of two factors, porcine somatotropin and graded levels of amino acids, on the total accumulation and the accretion rate of amino acids across a broad range of protein deposition rates in growing pigs. Treatments included 1) with or without a daily injection of porcine somatotropin and 2) graded levels of total dietary lysine from 0.75% to 1.50%. As expected, both the administration of porcine somatotropin and increased dietary lysine increased both the amount and the rate of amino acid accretion. However, the amount and rate of amino acid accretion from increased dietary amino acids were markedly greater in pigs treated with porcine somatotropin. Thus, the extent to which the genetic potential for protein deposition is achieved depends on both the anabolic capacity of the pig and the amino acid concentration of the diet provided.

Identification of cold acclimated genes in leaves of Citrus unshiu by mRNA differential display.

Citrus unshiu is freeze tolerant to -10 degrees C when fully acclimated after exposure to cold, nonfreezing temperatures. To gain an understanding of its cold tolerance mechanism, mRNA differential display reverse transcriptase polymerase chain reaction (DDRT-PCR) and quantitative relative RT-PCR were used to study gene expression under a gradual cold-acclimation temperature regime. Six up-regulated and two down regulated genes were identified based on their amino acid sequences. The identified proteins encoded by the up-regulated genes were: 14-3-3 protein, 40S ribosomal protein S23, putative 60S ribosomal protein L15, nucleoside diphosphate kinase III protein, regulator of chromosome condensation-like protein, and amino acid permease 6. The proteins encoded by the two down-regulated genes were: miraculin-like protein and beta-galactosidase. Their individual function has been briefly reviewed based on published information. In addition to the findings in this study, we compared the function of cold responsive genes of Poncirus trifoliata, a very cold hardy relative of Citrus species that is freeze tolerant to -30 degrees C when fully acclimated, to the function of genes in the current study.

Cold acclimation induced genes of trifoliate orange (Poncirus trifoliata).

Commercial citrus varieties are sensitive to low temperature. Poncirus trifoliata is a close relative of Citrus species and has been widely used as a cold-hardy rootstock for citrus production in low-temperature environments. mRNA differential display-reverse transcription (DDRT)-PCR and quantitative relative-RT-PCR were used to study gene expression of P. trifoliata under a gradual cold-acclimation temperature regime. Eight up-regulated cDNA fragments were isolated and sequenced. These fragments showed high similarities at the amino acid level to the following genes with known functions: betaine/proline transporter, water channel protein, aldo-keto reductase, early light-induced protein, nitrate transporter, tetratricopeptide-repeat protein, F-box protein, and ribosomal protein L15. These cold-acclimation up-regulated genes in P. trifoliata are also regulated by osmotic and photo-oxidative signals in other plants.