生物谷：在植物的生命周期诸如发芽期或开花期，植物完全可以根据外界环境条件的变化，调节自己的生长状况。而当环境不适合时，它们甚至可以暂时抑制自己的生长。那么，植物是如何1步步实现这种能力的呢？日前，世界著名的植物分子生物学实验室———约翰艾因斯中心的科学家在《当代生物期刊》上，宣称发现了植物是怎样在进化过程中逐渐获得适应环境与气候变化的能力的。
赤霉素是植物生长的重要激素。研究者通过多种植物在赤霉素信号传导途径中基因的变化情况来了解植物的`进化过程。最先进化的陆生植物是地钱类、金鱼藻类和原始地衣类等苔藓植物，这些物种大多数今天依然存在。它们可以复制自己的基因，但其本身的蛋白质却不具备互相交换信息的功能，也不具备抑制自我生长的能力。
40亿年前，石松类植物开始进化，并具有了植物维管组织，从而具有了在植物体内输送水分和营养物的功能，体内蛋白质也具有了互相交换信息的能力。然而它们尚不能抑制自我生长。直到30亿年前，裸子植物（开花植物）体内结构的变化允许蛋白质相互交换信息，并相应地调整基因的分布，最终在进化中获得了抑制自我生长的能力，因此裸子植物成为在当时占主导并且在今天种群依然庞大的物种。（科技日报）
原始出处:
Current Biology, Vol 17, 1225-1230, 17 July 2007
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Step-by-Step Acquisition of the Gibberellin-DELLA Growth-Regulatory Mechanism during Land-Plant Evolution
1 John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom
Corresponding author
Nicholas P. Harberd
Angiosperms (flowering plants) evolved relatively recently and are substantially diverged from early land plants (bryophytes, lycophytes, and others [1]). The phytohormone gibberellin (GA) adaptively regulates angiosperm growth via the GA-DELLA signaling mechanism [2, 3, 4, 5, 6, 7]. GA binds to GA receptors (GID1s), thus stimulating interactions between GID1s and the growth-repressing DELLAs [8, 9, 10, 11, 12]. Subsequent 26S proteasome-mediated destruction of the DELLAs promotes growth [13, 14, 15, 16, 17]. Here we outline the evolution of the GA-DELLA mechanism. We show that the interaction between GID1 and DELLA components from Selaginella kraussiana (a lycophyte) is GA stimulated. In contrast, GID1-like (GLP1) and DELLA components from Physcomitrella patens (a bryophyte) do not interact, suggesting that GA-stimulated GID1-DELLA interactions arose in the land-plant lineage after the bryophyte divergence (430 million years ago [1]). We further show that a DELLA-deficient P. patens mutant strain lacks the derepressed growth characteristic of DELLA-deficient angiosperms, and that both ssiana and P. patens lack detectable growth responses to GA. These observations indicate that early land-plant DELLAs do not repress growth in situ. However, S. kraussiana and P. patens DELLAs function as growth-repressors when expressed in the angiosperm Arabidopsis thaliana. We conclude that the GA-DELLA growth-regulatory mechanism arose during land-plant evolution and via independent stepwise recruitment of GA-stimulated GID1-DELLA interaction and DELLA growth-repression functions.
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