饲料中添加二苯乙烯苷对斑点叉尾鮰生长和体色的影响

在饲料中分别添加0、0.33%、0.67%、1.33%和2.67%的二苯乙烯苷(THSG)制成5种等氮等能试验饲料饲喂(15±0.5)g斑点叉尾鮰(Ictalurus punctatus)42 d,研究THSG对其生长和体色的影响。结果表明。饲料中添加THSG对斑点叉尾鮰增重率和存活率均无显著影响,仅在添加量为2.67%时,试验组的饵料系数显著高于对照组(P<0.05);然而,随着添加量的增加,鮰皮肤和血液酪氨酸酶活力、皮肤黑色素含量和黑色素分布量均有提高,其中0.33%和0.67%组皮肤中酪氨酸酶活力分别为10.4 U和10.7 U,显著高于对照组的7.86 U;黑色素分布量分别为8.16%和9.38%,显著高于对照组的5.01%(P<0.05)。     

稻瘟病菌对三环唑的敏感性检测技术与抗药性风险评估

研究了稻瘟病菌对三环唑敏感性的离体检测技术及其潜在抗药性风险。三环唑抑制菌丝黑色素生物合成的有效中浓度（EC50 H）和抑制附着胞黑色素化的最小抑制浓度（MIC A）都与活体条件下三环唑防治稻瘟病的EC50有很好的相关性,相关系数（R2）分别为0.8995和0.8244。但EC50 H比MIC A的稳定性和重复性更好,可用于离体检测稻瘟病菌对三环唑的敏感性。在2000年抗药性检测中检测到的最敏感菌株DY2和最不敏感菌株GY6的无性单孢后代对三环唑的敏感性不稳定,平均EC50分别为4.4968 μg/mL和5.4010 μg/mL,差异不显著,说明DY2和GY6对三环唑的敏感性差异可能不是由抗药性变异引起的。DY2和GY6经过20代的活体药剂筛选后, GY6的EC50没有显著升高;但DY2的敏感性有一定的下降,EC50为初始菌株的10.0倍,说明稻瘟病菌对三环唑仍然属于低抗药性风险。     

MC1R c.676A>G与山羊皮肤色素沉积的关系及其对黑色素合成的影响

为探讨山羊MC1R基因c.676A>G突变与山羊皮肤色素沉积的关系,及其对黑色素合成和cAMP信号通路下游色素相关基因表达的影响:一方面采用直接测序法检测酉州乌羊及其杂交后代群体(120个个体)MC1R基因c.676A>G的突变情况,用色差仪测量不同基因型个体的腹部皮肤色度值,分析c.676A>G突变与皮肤色素沉积的关系;另一方面,构建野生型(MC1R c.676A)和突变型(MC1R c.676G)真核表达载体,采用脂质体介导法转染到小鼠皮肤黑色素瘤细胞(B16-F10)中进行过表达,利用酶标仪检测各组细胞黑色素含量的差异,并通过实时荧光定量PCR方法检测各组细胞中cAMP信号通路下游色素相关基因(MITF、TYR、TYRP1、DCT)的表达差异性。结果显示:酉州乌羊及其杂交后代群体中,c.676A>G位点均以GG基因型占优势,不同基因型群体的皮肤色度值差异不显著(P>0.05)。MC1R突变组(MC1R c.676G)细胞中的黑色素含量极显著(P<0.05)高于MC1R野生组(MC1R c.676A)。MITF、TYRP1和DCT基因在MC1R突变组中的相对表达量极显著(P<0.01)高于野生组,TYR基因在MC1R突变组细胞中的相对表达量显著(P<0.05)高于野生组。综上,MC1R基因c.676A>G不直接影响山羊皮肤色素沉积,但MC1R c.676G能促进B16-F10细胞中黑色素的合成,也能促进cAMP信号通路下游MITF、TYR、TYRP1和DCT等基因的表达,推测MC1R基因c.676A>G与黑色素合成密切相关。     

Dietary aflatoxin B1 induces abnormal deposition of melanin in the corium layer of the chicken shank possibly via promoting the expression of melanin synthesis-related genes

San-Huang chicken is a high-quality breed in China with yellow feather, claw and break. However, the abnormal phenomenon of the yellow shank turning into green shank of San-Huang chicken has been a concern, as it seriously reduces the carcass quality and economic benefit of yellow-feathered broilers. In this study, the cause of this abnormal green skin in shank was systematically investigated. Physiological anatomy revealed that the abnormal skin in shank was primarily due to the deposition of melanin under the dermis. After analyzing multiple potential causes such as heredity (pedigree and genetic markers), environment (water quality monitoring) and feed composition (mycotoxin detection), excessive aflatoxin B1 (AFB1) in feed was screened, accompanied with a higher L-dihydroxy-phenylalanine (L-DOPA) (P<0.05) and melanin content (P<0.01). So it was speculated that excessive AFB1 might be the main cause of abnormal green skin in shank. Subsequently, the further results showed that a high concentration of AFB1 (>170 μg kg^–1) indeed induced the abnormal green skin in shank compared to the normal AFB1 content (<10 μg kg^–1), and the mRNA levels of TYR, TYRP1, MITE, MC1R and EDN3 genes related to melanin deposition would significantly up-regulate (P<0.01) and the content and activity of tyrosinase (TyR) significantly increased (P<0.05). At the same time, the content of L-DOPA and melanin deposition also increased significantly (P<0.01), which also confirmed the effect of excessive AFB1 on melanin deposition in skin of shank. Results of additional experiments revealed that the AFB1’s negative effect on melanin deposition in skin of shank could last for a longer time. Taken together, the results of this study explained the occurrence and possible mechanisms of the abnormal AFB1-related green skin in shank of chickens. Excessive AFB1 in diets increased the L-DOPA content and melanin abnormal deposition in the chicken shank possibly via promoting TyR content and activity, and the expression of melanin synthesis-related genes. Furthermore, our findings once again raised the alarm of the danger of AFB1 in the broiler production.     

黄河鲤酪氨酸酶基因的克隆、表达模式及定位分析

为探究Tyrosinase(Tyr)基因在黄河鲤体色形成中的作用,利用生物显微镜对黄河鲤黑色鳞片、银色鳞片、鳍条色素细胞的组成进行观察,并利用RACE克隆黄河鲤Tyr基因全长cDNA序列,荧光定量PCR分析其在不同组织中的表达情况,Western blot印迹和免疫组织化学方法检测其蛋白的表达定位。结果显示,黄河鲤具有黑色素细胞、黄色素细胞和虹彩细胞3种色素细胞,3种色素细胞的数量、种类和分布在不同组织中存在较大差异。黄河鲤Tyr基因cDNA全长1717 bp(GenBank ID:No.KY305667),其中ORF长1605 bp,编码535个氨基酸,5′-UTR区41 bp,3′-UTR区71 bp。蛋白同源分析发现,黄河鲤Tyr与鲤科鱼类相似性最高,与哺乳类及鸟类等脊椎动物相似性最低。系统进化分析显示,黄河鲤Tyr与鲤、瓯江彩鲤、锦鲤和斑马鱼等鲤科鱼类的亲缘关系最近。实时定量PCR分析表明,Tyr基因在黄河鲤不同组织中均有表达,肌肉中的表达量最高,其次是黑色皮肤,另外在黄色皮肤、臀鳍和尾鳍等黑色素细胞存在的组织中也有较高表达。Western blot印迹结果显示,Tyr基因在黑色皮肤中表达最高,其次是臀鳍和尾鳍,银色皮肤中没有表达。免疫组织化学结果显示,Tyr基因在黑色皮肤的黑色素细胞和黏液细胞中有表达。研究表明,Tyr基因表达水平与黑色素细胞数量和分布具有一定相关性,参与黄河鲤体色的形成。