RESUMEN
Shade caused by the proximity of neighboring vegetation triggers a set of acclimation responses to either avoid or tolerate shade. Comparative analyses between the shade-avoider Arabidopsis thaliana and the shade-tolerant Cardamine hirsuta revealed a role for the atypical basic-helix-loop-helix LONG HYPOCOTYL IN FR 1 (HFR1) in maintaining the shade tolerance in C. hirsuta, inhibiting hypocotyl elongation in shade and constraining expression profile of shade-induced genes. We showed that C. hirsuta HFR1 protein is more stable than its A. thaliana counterpart, likely due to its lower binding affinity to CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), contributing to enhance its biological activity. The enhanced HFR1 total activity is accompanied by an attenuated PHYTOCHROME INTERACTING FACTOR (PIF) activity in C. hirsuta. As a result, the PIF-HFR1 module is differently balanced, causing a reduced PIF activity and attenuating other PIF-mediated responses such as warm temperature-induced hypocotyl elongation (thermomorphogenesis) and dark-induced senescence. By this mechanism and that of the already-known of phytochrome A photoreceptor, plants might ensure to properly adapt and thrive in habitats with disparate light amounts.
Asunto(s)
Aclimatación/genética , Proteínas de Arabidopsis/genética , Arabidopsis/genética , Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica de las Plantas/genética , Transcripción Genética/genética , Secuencia de Bases , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Hipocótilo/genética , Fitocromo/genéticaRESUMEN
The AROM complex is a multifunctional metabolic machine with ten enzymatic domains catalyzing the five central steps of the shikimate pathway in fungi and protists. We determined its crystal structure and catalytic behavior, and elucidated its conformational space using a combination of experimental and computational approaches. We derived this space in an elementary approach, exploiting an abundance of conformational information from its monofunctional homologs in the Protein Data Bank. It demonstrates how AROM is optimized for spatial compactness while allowing for unrestricted conformational transitions and a decoupled functioning of its individual enzymatic entities. With this architecture, AROM poses a tractable test case for the effects of active site proximity on the efficiency of both natural metabolic systems and biotechnological pathway optimization approaches. We show that a mere colocalization of enzymes is not sufficient to yield a detectable improvement of metabolic throughput.
