ACKNOWLEDGEMENTS
We thank Ivone Torres-Jerez (Noble Research Institute) for technical lab support including isolation and purification of RNA, David Huhman and Bonnie Watson (Noble Research Institute) for assistance with acquisition and analysis of GC-MS data, Nick Krom and Yuhong Tang (Noble Research Institute) for help with production and processing of RNA-Seq data, as well as Jin Nakashima and Jaydeep Kolape (Noble Research Institute) for technical assistance with collection of root architectural traits. We also thank Kelly Craven, Malay Saha, Yuan Wang (Noble Research Institute), Jennifer Pett-Ridge (Lawrence Livermore National Laboratory) and Mary Firestone (University of California, Berkeley) for discussions.