Verification of QTL for grain starch content and its genetic correlation with oil content using two connected RIL populations in high-oil maize.

Grain oil content is negatively correlated with starch content in maize in general. In this study, 282 and 263 recombinant inbred lines (RIL) developed from two crosses between one high-oil maize inbred and two normal dent maize inbreds were evaluated for grain starch content and its correlation with oil content under four environments. Single-trait QTL for starch content in single-population and joint-population analysis, and multiple-trait QTL for both starch and oil content were detected, and compared with the result obtained in the two related F(2∶3) populations. Totally, 20 single-population QTL for grain starch content were detected. No QTL was simultaneously detected across all ten cases. QTL at bins 5.03 and 9.03 were all detected in both populations and in 4 and 5 cases, respectively. Only 2 of the 16 joint-population QTL had significant effects in both populations. Three single-population QTL and 8 joint-population QTL at bins 1.03, 1.04-1.05, 3.05, 8.04-8.05, 9.03, and 9.05 could be considered as fine-mapped. Common QTL across F(2∶3) and RIL generations were observed at bins 5.04, 8.04 and 8.05 in population 1 (Pop.1), and at bin 5.03 in population 2 (Pop.2). QTL at bins 3.02-3.03, 3.05, 8.04-8.05 and 9.03 should be focused in high-starch maize breeding. In multiple-trait QTL analysis, 17 starch-oil QTL were detected, 10 in Pop.1 and 7 in Pop.2. And 22 single-trait QTL failed to show significance in multiple-trait analysis, 13 QTL for starch content and 9 QTL for oil content. However, QTL at bins 1.03, 6.03-6.04 and 8.03-8.04 might increase grain starch content and/or grain oil content without reduction in another trait. Further research should be conducted to validate the effect of these QTL in the simultaneous improvement of grain starch and oil content in maize.

[Effect of insulin on burn wound healing in aging diabetes mellitus rats].

OBJECTIVE: To investigate the effect of topical application of insulin on the burn wound healing in aging diabetes mellitus (DM) rats and to explore its mechanism. METHODS: Seventy-five SPF Wistar rats (female and/or male), aged 12-24 months and weighing 300-350 g, were selected and randomly divided into group A (burn control group, n=25), group B (DM burn control group, n=25), and group C (DM insulin treatment group, n=25). The rats in group B and group C were fed with high-fat, high-protein, and high-sugar forage for 1 month and received intraperitoneal injection of streptozotocin (STZ) to establish experimental model of aging DM. The rats were fed with high-fat, high-protein, and high-sugar forage for another 8 weeks. Then, the deep second-degree burn model was established in the rats of group B and group C. The wounds in group A and B underwent local subcutaneous injection of 2 mL isotonic saline and group C received local subcutaneous injection of 0.1 U insulin. The rate of wound healing was calculated 7, 14, and 21 days after burn injury. At 1, 3, 7, 14, and 21 days after burn injury, HE staining observation, immunohistochemistry staining for CD34, detection of sugar and hydroxyproline (HOP) content in wound tissue, and microvessel density (MVD) calculation were performed. RESULTS: At 7, 14, and 21 days after burn injury, the wound healing rates of group A and group C was significantly higher than that of group B (P < 0.05), and there was no significant difference between group A and group C (P > 0.05). Histology observation at 21 days after burn injury: in group A, certain degree of epithelization was evident in the wound epithelium; in group B, large quantity of necrotic tissue was evident; in group C, complete epithelization occurred in the wound epithelium with better epithelial cell differentiation and more neonatal collagen. For the sugar content in the wound tissue, group A was significantly lower than group B or group C at 1, 3, 7, 14, and 21 days (P < 0.05) and group C was significantly lower than group B at 7, 14, and 21 days (P < 0.05). For the HOP content in the wound tissue and the MVD count, group A or group C was significantly higher than group B (P < 0.05) and there was no significant difference between group A and group C (P > 0.05). CD34 expression: in group A, it was (+) at 7 days, (++) at 14 days, and (+++) at 21 days; in group B, it was (+) at 14 and 21 days; in group C, it was (++) at 7 days and (+++) at 14 and 21 days. CONCLUSION: Topical application of insulin can promote the synthesis of wound collagen, accelerate the wound angiogenesis, and speed up the wound healing in aging DM rats.