A regulatory role for proline metabolism in stimulating Arabidopsis thaliana seed germination

Analysis of the rate-limiting dehydrogenases of the oxidative pentosephosphate pathway (OPPP), as well as changes in the contributions of¹⁴C₁- and ¹⁴C₆-labelled glucose torespired CO₂ during germination, indicated activation of the OPPPduring Arabidopsis seed germination. An approximatelyfour-fold increase in free proline (Pro) was also observed prior to radicleemergence in most seeds. Delayed radicle emergence in transgenicArabidopsis seeds which expressed an antisense copy of thegene encoding the Pro biosynthetic enzyme¹-pyrroline-5-carboxylate synthetase correlated with anapproximately 35% reduction in the maximal concentration of Pro accumulated bythe antisense lines during germination. A dose-dependent inhibition ofArabidopsis seed germination by millimolar concentrationsof Pro capable of feedback inhibition of Pro synthesis reinforced the role ofPro synthesis in promoting germination. The ability of the artificial oxidantsmethylene blue and phenazine ethosulphate to overcome the inhibitory effects ofPro suggests a functional link between elevated Pro synthesis and increasedOPPPactivity and the importance of coupling of both pathways in stimulatinggermination.     

小鼠内耳发育核心转录因子的保守性及调控网络的比较分析

在脊椎动物内耳发育中, Six1、Six4、Pax2、Pax8、Foxi1、Dlx5、Gbx2、Irx2/3、Msx1等基因作为核心调控基因参与听基板的诱导过程。文章通过生物信息学方法, 对小鼠内耳发育的核心转录因子进行保守性分析并研究其相互调控关系, 得到小鼠内耳发育过程中核心转录因子的基因调控网络。与文献中已知的小鼠内耳发育基因调控关系相比, Pax2、Pax8、Foxi1、Dlx5基因在内耳发育中仍然起主要调控者的角色, Six1则处于被多个转录因子调节的地位, Gbx2、Irx2/3、Msx1在调控网络中也起到重要作用。对出现的差异进行了合理的分析, 同时结合构建的调控网络预测了可能存在的Msx1对Six1、Gbx2的调控作用。序列预测结果也发现了一些新的调控关系, 所涉及的转录因子包括Sox5、Lhx2、Rax、Otx1、Otx2、Pitx1、Pitx2、Nkx2-5、Irx4、Irx6、Dlx2、Hmx1/2/3、Pou4f3、Pax4、Tlx2。文章为深入了解内耳发育调控机制提供了基础信息。