西藏特有植物砂生槐天然居群遗传多样性研究

采用等位酶淀粉凝胶电泳技术对西藏雅鲁藏布江中游砂生槐 (Sophoramoorcroftiana) 10个天然居群的遗传多样性进行了研究。 13个酶系统 2 4个酶位点 ( 46个等位基因 )的检测结果表明 ,砂生槐具较低的遗传变异水平。居群水平上的遗传多样性指标分别为 :多态位点百分率Pp =2 5 .0 %～ 37.5 % ,等位基因平均数Ap=1.3～ 1.7,平均期望杂合度Hep=0 .112～ 0 .16 9;种水平上的遗传多样性 (Ps=37.5 % ,As=1.9,Hes=0 .171)低于长寿命木本被子植物的平均值 (Ps=5 9.5 % ,As=2 .10 ,Hes=0 .183)。居群遗传结构的分析显示 ,10个居群中随机交配的偏差为FIS=- 0 .0 0 71,表明砂生槐在居群水平上存在轻微的杂合子过量现象 ,偏离了Hardy Weinberg平衡 ;FST=0 .1748,表明砂生槐是居群间分化较大的一类多年生木本植物 ,主要原因是环境恶化和人类活动干扰 (过度砍伐、放牧等 )导致其生境片断化 ,从而影响了居群间基因交流而造成基因流水平较低 (Nm =1.180 2 )。砂生槐高海拔居群H2 (谢通门 )、H31(江当 1)��H32 (江当 2 )、H5 (朗塞岭 )包含着绝大部分等位基因 ,显示了相对较高的遗传多样性水平 ,应加以保护和管理 ,作为砂生槐种质资源就地保存的基地。

Cys-92, Cys-95, and the C-terminal 12 residues of the Vibrio harveyi ferric uptake regulator (Fur) are functionally inessential

Ferric uptake regulator (Fur) is a global regulator involved in multiple aspects of bacterial life. The gene encoding the Vibrio harveyi Fur (Fur(vh)) was cloned from a pathogenic V. harveyi strain isolated from diseased fish. Furvh shares 77% overall sequence identity with the Escherichia coli Fur (Fur(Ec)) and could complement a mutant of Fur(Ec). Like Fur(Ec), Fur(Vh), possesses two cysteine residues at positions 92 and 95, yet unlike Fur(Ec), in which these cysteine residues constitute part of the metal ion coordination site and hence are vital to the repressor activity, C92 and C95 of Fur(Vh) proved to be functionally inessential. Further study identified a Vibrio Fur signature sequence, which is preserved in all the ten Vibrio Fur proteins that have been discovered to date but in none of the non-vibrio Fur proteins. Site-directed and random mutation analyses of the signature residues, the cysteine residues, and seven highly charged amino acid residues indicated that D9, H32, C137, and K138 of Fur(vh) are functionally important but D9, C137, and K138 can be replaced by more than one functional substitutes. Systematic deletion analysis demonstrated that the C-terminal 12 residues of Fur(Vh) are functionally inessential. These results (i) indicated that the activation mechanism, or certain aspects of which, of Fur(Vh) is possibly different from that of Fur(Ec); and (ii) suggested that it is not very likely that the C-terminal 12 residues play any significant role in the activation or stability of Fur(Vh); and (iii) provided insights into the potential function of the local structure involving C137 and K138.