SBRC-Nottingham: sustainable routes to platform chemicals from C1 waste gases.

Synthetic Biology Research Centre (SBRC)-Nottingham (www.sbrc-nottingham.ac.uk) was one of the first three U.K. university-based SBRCs to be funded by the Biotechnology and Biological Sciences Research Council (BBSRC) and Engineering and Physical Sciences Research Council (EPSRC) as part of the recommendations made in the U.K.'s Synthetic Biology Roadmap. It was established in 2014 and builds on the pioneering work of the Clostridia Research Group (CRG) who have previously developed a range of gene tools for the modification of clostridial genomes. The SBRC is primarily focussed on the conversion of single carbon waste gases into platform chemicals with a particular emphasis on the use of the aerobic chassis Cupriavidus necator.

Regulation and manipulation of ABA biosynthesis in roots.

Overexpression of 9-cis-epoxycarotenoid dioxygenase (NCED) is known to cause abscisic acid (ABA) accumulation in leaves, seeds and whole plants. Here we investigated the manipulation of ABA biosynthesis in roots. Roots from whole tomato plants that constitutively overexpress LeNCED1 had a higher ABA content than wild-type (WT) roots. This could be explained by enhanced in situ ABA biosynthesis, rather than import of ABA from the shoot, because root cultures also had higher ABA content, and because tetracycline (Tc)-induced LeNCED1 expression caused ABA accumulation in isolated tobacco roots. However, the Tc-induced expression led to greater accumulation of ABA in leaves than in roots. This demonstrates for the first time that NCED is rate-limiting in root tissues, but suggests that other steps were also restrictive to pathway flux, more so in roots than in leaves. Dehydration and NCED overexpression acted synergistically in enhancing ABA accumulation in tomato root cultures. One explanation is that xanthophyll synthesis was increased during root dehydration, and, in support of this, dehydration treatments increased beta-carotene hydroxylase mRNA levels. Whole plants overexpressing LeNCED1 exhibited greatly reduced stomatal conductance and grafting experiments from this study demonstrated that this was predominantly due to increased ABA biosynthesis in leaves rather than in roots. Genetic manipulation of both xanthophyll supply and epoxycarotenoid cleavage may be needed to enhance root ABA biosynthesis sufficiently to signal stomatal closure in the shoot.