The meta-hydroxylation step in the phenylpropanoid pathway: a new level of complexity in the pathway and its regulation

Together in silico and genetic mining approaches have recently designated the CYP98 family of plant cytochromes P450 as the family of enzymes that catalyzes the meta-hydroxylation step in the phenylpropanoid pathway. This meta-hydroxylation is not catalyzed on the free p-coumaric acid as anticipated, but on its conjugates with shikimic, quinic, or phenyllactic acids. While all CYP98s have in common phenol meta-hydroxylase activity, p-coumaroylshikimate remains their preferred substrate. High expression of CYP98s is detected in lignifying tissues in stems, roots, and siliques. The CYP98A3 gene disruption in Arabidopsis thaliana leads to a drastic inhibition of lignin synthesis, cell growth, and plant development. The meta-hydroxylation of phenolic precursors is thus essential for higher plant development. Isolation of coding sequences belonging to the CYP98 family from basil, wheat, and extensive functional analysis of the recombinant enzymes, together with CYP98s from other plant taxa, helps shedding some light on mechanisms of P450s evolution. Most importantly, the occurrence of the meta-hydroxylation on esters of shikimic or quinic acids introduces a new biochemical regulation mechanism in the phenylpropanoid pathway.     

When does quality of relationships with coworkers predict burnout over time? The moderating role of work motivation

The present prospective study examines the interplay between the quality of relationships with coworkers and work motivation in predicting burnout. Considering self-determined motivation at work as a potential moderator, we investigated whether relationships with coworkers are equally important to all employees in preventing burnout. A total of 533 college employees participated in this study. Data were collected at two time points, two years apart. Results from structural equation modeling indicated negative main effects for high-quality relationships and self-determined motivation on burnout. A significant interaction effect between these two factors on burnout was also revealed, suggesting that high-quality relationships with coworkers is crucial for those employees who exhibit less self-determined work motivation. Implications for burnout research and management practices are discussed (Deci & Ryan, 1985 ). Copyright © 2009 John Wiley & Sons, Ltd.