Friday April 11 2008
CEA
To provide deeper insight into this phenomenon, researcher from the IBS-led Protein Crystallogenesis and Crystallography Laboratory working with American, Swedish and Argentinean research teams identified several genes in Arabidopsis that are involved in shade avoidance syndrome. They have shown that mutations in these genes lead to different responses in shade-grown plants. One of these genes encodes a peculiar enzyme called TAA1. The teams were able to resolve TAA1 at atomic scale and characterize its active site. They were also able to demonstrate that TAA1 catalyzes tryptophan conversion during the first step in a novel biosynthesis pathway of the auxin phytohormone. It thus appears that plants rapidly deploy this pathway to synthesize auxin at the high levels needed to trigger the changes involved in ‘shade-avoidance syndrome’.
In intensive agriculture settings, shade avoidance syndrome has a significant impact on both the quantity and quality of biomass produced. Understanding the molecular mechanisms underlying the deployment of this shade avoidance strategy thus represents the first step towards improving the plants being farmed in modern-day intensive crop-based agricultural systems.
How plants get out of the shade
CEA
Intensively-farmed plants growing competitively side-by-side fight one another to get the most sunlight possible. If they are able to do this, it is because they have developed a series of responses called “shade-avoidance syndrome”. What biological mechanism(s) can enable these plants to boost their growth and dominate their neighbours? This is the question that prompted the work led by researchers from the Jean-Pierre Ebel Institute of Structural Biology (IBS, a joint CEA-CNRS-Joseph Fourier University institute) together with American, Swedish and Argentinean teams. Their latest results, which have just been published in Cell, open up perspectives for agronomics research.
The phenomena at work as plants battle for the best sunlight are easily observed and clearly identifiable. Plants grown at high densities use their various photoreceptors to perceive spectrum alterations resulting from the absorption of red light by canopy leaves and the reflection of far-red light from neighbouring plants. These changes in light quality trigger a series of responses known collectively as ‘shade-avoidance syndrome’. Several indicators show that shade avoidance is at work: stems elongating at the expense of leaves, storage organs expanding, branching is inhibited, and flowering is accelerated.
To provide deeper insight into this phenomenon, researcher from the IBS-led Protein Crystallogenesis and Crystallography Laboratory working with American, Swedish and Argentinean research teams identified several genes in Arabidopsis that are involved in shade avoidance syndrome. They have shown that mutations in these genes lead to different responses in shade-grown plants. One of these genes encodes a peculiar enzyme called TAA1. The teams were able to resolve TAA1 at atomic scale and characterize its active site. They were also able to demonstrate that TAA1 catalyzes tryptophan conversion during the first step in a novel biosynthesis pathway of the auxin phytohormone. It thus appears that plants rapidly deploy this pathway to synthesize auxin at the high levels needed to trigger the changes involved in ‘shade-avoidance syndrome’.
In intensive agriculture settings, shade avoidance syndrome has a significant impact on both the quantity and quality of biomass produced. Understanding the molecular mechanisms underlying the deployment of this shade avoidance strategy thus represents the first step towards improving the plants being farmed in modern-day intensive crop-based agricultural systems.
Reference :
Yi Tao, Jean-Luc Ferrer, Karin Ljung, Florence Pojer, Fangxin Hong, Jeff A. Long, Lin Li, Javier E. Moreno, Marianne E. Bowman, Lauren J. Ivans, Youfa Cheng, Jason Lim, Yunde Zhao, Carlos L. Ballaré , Göran Sandberg, Joseph P. Noel, and Joanne Chory. Rapid Synthesis of Auxin via a New Tryptophan-Dependent Pathway Is Required for Shade Avoidance in Plants. Cell (2008), 133: 164–176.
*tryptophane is one of the twenty amino acid constituting proteins