A light-sensitive mechanism differently regulates transcription and transcript stability of ω3 fatty-acid desaturases (FAD3 , FAD7 and FAD8 ) in soybean photosynthetic cell suspensions

Abstract

The definitive version is available at:\ud \ud http://www.sciencedirect.com/science/journal/00145793The ω3 fatty-acid desaturases: FAD7 and FAD8 (plastid) and FAD3 (reticular) are responsible for trienoic fatty-acid (TA) production in plants. The expression of these enzymes seemed to be regulated differently in response to light. Darkness leads to a decrease in total TA level. Under such conditions, FAD3 and FAD8 transcript levels were undetectable but increased after re-illumination concomitant with TA levels, indicating a transcriptional control. On the contrary, FAD7 transcript levels were similar to illuminated control cells, suggesting the presence of a post-transcriptional control mechanism. Furthermore, FAD7 mRNA stability increased dramatically in darkness. Analysis of FAD7 protein accumulation using specific antibodies revealed that FAD7 was very stable whatever the light or darkness conditions. These results indicate that FAD7 enzyme availability is not limiting for 18:3 production in darkness. Our data point to an additional post-translational regulatory mechanism that controls the activity of FAD7 in response to light.The SB-P line [25] was kindly provided by Prof. Jack M. Widholm (University of Illinois at Urbana-Champaign, IL, USA).\ud \ud R.C. was recipient of a predoctoral fellowship from the Gobierno de Aragón. M.A. was recipient of a Ramon y Cajal Contract from the Ministry of Education and Science of Spain. This work was supported by the Ministry of Education and Science of Spain (Grants BMC2002-00031 and BMC2005-07422-C02-01).Peer reviewe