Putative role of γ -aminobutyric acid (GABA) as a long-distance signal in up-regulation of nitrate uptake in Brassica napus L.

The relationship between nitrate influx, BnNrt2 nitrate transporter gene expression and amino acid composition of phloem exudate was investigated during N‐deprivation (short‐term experiment) and over a growth cycle (long‐term experiment) in Brassica napus L. The data showed a positive correlation between γ‐aminobutyric acid (GABA) in phloem exudate and nitrate uptake in the short‐ and the long‐term experiments. The hypothesis that this non‐protein amino acid could up‐regulate nitrate uptake via a long‐distance signalling pathway was tested by providing an exogenous GABA supply to the roots. The effect of GABA was compared with the effects of Gln, Glu and Asn, each known to be inhibitors of nitrate uptake. The results showed that GABA treatment induced a significant increase of BnNrt2 mRNA expression, but had less effect on nitrate influx. By contrast, Gln, Glu and Asn significantly reduced nitrate influx and BnNrt2 mRNA expression compared with the control plants. This study provides the first evidence that GABA may act as a putative long‐distance inter‐organ signal molecule in plants in conjunction with negative control exerted by Gln. The up‐regulation effect of GABA on nitrate uptake is discussed in the context of its role in N metabolism, nutritional stress and the recent discovery of a putative role of GABA as a signal molecule in plant development.     

MLB-200型Q-开关Nd:YAG激光治疗雀斑67例疗效观察

本文报道使用MLB－200型Q－开关Nd:YAG激光治疗67例雀斑的疗效。选用532nm波长,光斑直径2－3mm,能量密度6－10J/cm^2,脉冲频率2－5次／秒,光斑重叠不超过10％。术后8周进行第二次治疗,第二次治疗后三个月评定疗效。结果,两次治疗后总痊愈率为92．545,无严重副作用产生。     

外源DNA在体内的吸收与降解

外源ＤＮＡ在动物体内的吸收与降解研究已经受到了关注[1、2 ] 。由于基因治疗与ＤＮＡ疫苗的飞速发展 ,经常要通过一定的方式将外源的ＤＮＡ导入到动物体 ,然而对于它们的吸收与降解机制到目前为止仍然不是十分清楚。用基因治疗疾病时 ,须解决外源基因在动物体内的吸收与降解问题 ,尤其是大量外源ＤＮＡ质粒在动物体内的吸收与降解问题。外源ＤＮＡ的吸收与降解研究已成为一个热点 ,目前主要集中在肠胃道吸收降解和细胞吸收降解两个方面。1 .外源ＤＮＡ在肠胃道中的吸收与降解最有可能让外源ＤＮＡ进入动物体的就是肠胃道 ,在每天的进食中 …     

多效唑（MET）对啤酒花试管苗生长和移栽的影响

在培养基中加入0.1-0.2mg/L浓度的多效唑（MET）,啤酒花试管苗植株矮壮,单株生根数量增加、移栽成活率提高13％。0．5－2．0mg/L时,试管苗基部愈伤组织增多,枝叶失绿,生长受到抑制。初步发现多将唑对啤酒花试管苗的效力与葡萄糖用量呈正相关。