背景回顾：During germination, seed reserves are mobilized to sustain the metabolic and energetic demands of plant growth. Mitochondrial respiration is presumably required to drive germination in several species, but only recently its role in this process has begun to be elucidated. 

主要研究：Using Arabidopsis thaliana lines with changes in the levels of the respiratory chain component cytochrome c (CYTc), we investigated the role of this protein in germination and its relation with hormonal pathways. 

结果1-CYTc不足延迟种子萌发：CYTc deficiency causes delayed seed germination, which correlates with decreased cyanide-sensitive respiration and ATP production at the onset of germination. 

结果2-CYTC-2受ABA抑制：In addition, CYTc affects the sensitivity of germination to abscisic acid (ABA), which negatively regulates the expression of CYTC-2, one of two CYTc-encoding genes in Arabidopsis. 

结果3-ABI4直接负调控CYTC-2的表达：CYTC-2 acts downstream of the transcription factor ABSCISIC ACID INSENSITIVE 4 (ABI4), which binds to a region of the CYTC-2 promoter required for repression by ABA and regulates its expression. 

结论：The results show that CYTc is a main player during seed germination through its role in respiratory metabolism and energy production. In addition, the direct regulation of CYTC-2 by ABI4 and its effect on ABA-responsive germination establishes a link between mitochondrial and hormonal functions during this process.

 摘 要 

在种子萌发过程中，植物会调用种子中的储存物资，以维持其生长的代谢和能量需求。据推测，一些植物的种子萌发需要线粒体呼吸来进行驱动，但直到最近，人们才逐步阐明其在种子萌发过程中的作用。利用呼吸链成分细胞色素c （CYTc）水平存在变异的拟南芥株系，作者研究了该蛋白在种子萌发中的作用以及其与植物激素途径之间的关系。CYTc不足会导致种子萌发的延迟，这与萌发开始时氰化物敏感呼吸和ATP生成的减少有关。此外，CYTc影响种子萌发对脱落酸（ABA）的敏感性，而ABA能够负调控拟南芥中两个编码CYTc蛋白的基因之一，即CYTc-2的表达。CYTC-2基因作用于转录因子ABI4的下游，ABI4能够结合到CYTC-2启动子区并以ABA依赖型的方式调控后者的表达水平。结果表明，CYTc通过其在呼吸代谢和能量产生中的作用，在种子萌发过程中起主要作用。此外，ABI4对CYTC-2基因的直接调节作用及其在ABA响应的种子萌发中的作用，从而建立了线粒体和激素功能之间在种子萌发这一生物学过程中的联系。