Current Biology：植物適應環境變化的機理
畢業
生物谷：在植物的生命周期諸如發芽期或開花期，植物完全可以根據外界環境條件的變化，調節自己的生長狀況。而當環境不適合時，它們甚至可以暫時抑制自己的生長。那么，植物是如何1步步實現這種能力的呢？日前，世界著名的植物分子生物學實驗室———約翰艾因斯中心的科學家在《當代生物期刊》上，宣稱發現了植物是怎樣在進化過程中逐漸獲得適應環境與氣候變化的能力的。
赤霉素是植物生長的重要激素。研究者通過多種植物在赤霉素信號傳導途徑中基因的變化情況來了解植物的進化過程。最先進化的陸生植物是地錢類、金魚藻類和原始地衣類等苔蘚植物，這些物種大多數今天依然存在。它們可以復制自己的基因，但其本身的蛋白質卻不具備互相交換信息的功能，也不具備抑制自我生長的能力。
40億年前，石松類植物開始進化，并具有了植物維管組織，從而具有了在植物體內輸送水分和營養物的功能，體內蛋白質也具有了互相交換信息的能力。然而它們尚不能抑制自我生長。直到30億年前，裸子植物（開花植物）體內結構的變化允許蛋白質相互交換信息，并相應地調整基因的分布，最終在進化中獲得了抑制自我生長的能力，因此裸子植物成為在當時占主導并且在今天種群依然龐大的物種。（科技日報）
原始出處:
Current Biology, Vol 17, 1225-1230, 17 July 2007
Report
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
nicholas.harberd@bbsrc.ac.uk
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 S.kraussiana 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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