LATERAL BRANCHING OXIDOREDUCTASEacts in the final stages of strigolactone biosynthesis inArabidopsis

Abstract

Strigolactones are a group of plant compounds of diverse but related chemical structures. They have similar bioactivity across a broad range of plant species, act to optimize plant growth and development, and promote soil microbe interactions. Carlactone, a common precursor to strigolactones, is produced by conserved enzymes found in a number of diverse species. Versions of the MORE AXILLARY GROWTH1 (MAX1) cytochrome P450 from rice and Arabidopsis thaliana make specific subsets of strigolactones from carlactone. However, the diversity of natural strigolactones suggests that additional enzymes are involved and remain to be discovered. Here, we use an innovative method that has revealed a missing enzyme involved in strigolactone metabolism. By using a transcriptomics approach involving a range of treatments that modify strigolactone biosynthesis gene expression coupled with reverse genetics, we identified LATERAL BRANCHING OXIDOREDUCTASE (LBO), a gene encoding an oxidoreductase-like enzyme of the 2-oxoglutarate and Fe(II)-dependent dioxygenase superfamily. Arabidopsis lbo mutants exhibited increased shoot branching, but the lbo mutation did not enhance the max mutant phenotype. Grafting indicated that LBO is required for a graft-transmissible signal that, in turn, requires a product of MAX1. Mutant lbo backgrounds showed reduced responses to carlactone, the substrate of MAX1, and methyl carlactonoate (MeCLA), a product downstream of MAX1. Furthermore, lbo mutants contained increased amounts of these compounds, and the LBO protein specifically converts MeCLA to an unidentified strigolactone-like compound. Thus, LBO function may be important in the later steps of strigolactone biosynthesis to inhibit shoot branching in Arabidopsis and other seed plants.plant | branching | strigolactone | biosynthesis | Arabidopsis

Phloem Transport of the Receptor DWARF14 Protein Is Required for Full Function of Strigolactones

“…Otherwise, the mobility of the D14 protein and/or the dependence of its function on its transport may differ between species. Certainly these species are diverse with respect to other aspects of SL biosynthesis and response (Brewer et al, 2015(Brewer et al, , 2016Dun et al, 2012;Guan et al, 2012;Mashiguchi et al, 2009;Minakuchi et al, 2010;Shinohara et al, 2013;Yoneyama et al, 2012).…”

Strigolactone regulates shoot development through a core signalling pathway

“…This pathway is responsible for most SL synthesis, but plants lacking any one of these enzymes still produce some SLs, indicating that our knowledge of SL synthesis is incomplete (Waldie et al, 2014). Recent work suggests that there are likely to be multiple additional enzymes responsible for the further processing of carlactone into various active SLs (Brewer et al, 2016). Much recent progress has been made in understanding SL signalling (reviewed in Bennett and Leyser, 2014; Waldie et al, 2014).…”

StrigoQuant: A genetically encoded biosensor for quantifying strigolactone activity and specificity

“…Carlactone is oxidized by cytochrome P450 enzymes (clade711; MAX1 in Arabidopsis ) to carlactonoic acid ( 17 ), to 4-deoxyorobanchol (4DO), and further to orobanchol ( 18 ). After methylation, carlactonoic acid is converted in Arabidopsis by an oxoglutarate-dependent dioxygenase (lateral branching oxidoreductase) into a yet unidentified product needed to inhibit shoot branching ( 19 ). …”