title: A toolbox of genes, proteins, metabolites and promoters for improving drought tolerance in soybean includes the metabolite coumestrol and stomatal development genes.
abstract: BACKGROUND
  The purpose of this project was to identify metabolites, proteins, genes, and promoters associated with water stress responses in soybean. A number of these may serve as new targets for the biotechnological improvement of drought responses in soybean (Glycine max).
  
  
  RESULTS
  We identified metabolites, proteins, and genes that are strongly up or down regulated during rapid water stress following removal from a hydroponics system. 163 metabolites showed significant changes during water stress in roots and 93 in leaves. The largest change was a root-specific 160-fold increase in the coumestan coumestrol making it a potential biomarker for drought and a promising target for improving drought responses. Previous reports suggest that coumestrol stimulates mycorrhizal colonization and under certain conditions mycorrhizal plants have improved drought tolerance. This suggests that coumestrol may be part of a call for help to the rhizobiome during stress. About 3,000 genes were strongly up-regulated by drought and we identified regulators such as ERF, MYB, NAC, bHLH, and WRKY transcription factors, receptor-like kinases, and calcium signaling components as potential targets for soybean improvement as well as the jasmonate and abscisic acid biosynthetic genes JMT, LOX1, and ABA1. Drought stressed soybean leaves show reduced mRNA levels of stomatal development genes including FAMA-like, MUTE-like and SPEECHLESS-like bHLH transcription factors and leaves formed after drought stress had a reduction in stomatal density of 22.34 % and stomatal index of 17.56 %. This suggests that reducing stomatal density may improve drought tolerance. MEME analyses suggest that ABRE (CACGT/CG), CRT/DRE (CCGAC) and a novel GTGCnTGC/G element play roles in transcriptional activation and these could form components of synthetic promoters to drive expression of transgenes. Using transformed hairy roots, we validated the increase in promoter activity of GmWRKY17 and GmWRKY67 during dehydration and after 20 μM ABA treatment.
  
  
  CONCLUSIONS
  Our toolbox provides new targets and strategies for improving soybean drought tolerance and includes the coumestan coumestrol, transcription factors that regulate stomatal density, water stress-responsive WRKY gene promoters and a novel DNA element that appears to be enriched in water stress responsive promoters.
authors: Department of Biology and Microbiology, South Dakota State University, Brookings, SD57007, USA. tprateek@dornsife.usc.edu.|Current address, Molecular and Computational Biology, Dana & David Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA, 90089, USA. tprateek@dornsife.usc.edu.
authors: Prateek
authors: P
authors: Tripathi
authors: Department of Biology and Microbiology, South Dakota State University, Brookings, SD57007, USA. roel.rabara@tamu.edu.|Current address: Texas A&M AgriLife Research and Extension Center, Dallas, TX, 75252, USA. roel.rabara@tamu.edu.
authors: Roel C
authors: RC
authors: Rabara
authors: Department of Biology and Microbiology, South Dakota State University, Brookings, SD57007, USA. Neil.Reese@sdstate.edu.
authors: R Neil
authors: RN
authors: Reese
authors: Texas A&M AgriLife Research and Extension Center, Dallas, TX, 75252, USA. Marissa.Miller@ag.tamu.edu.
authors: Marissa A
authors: MA
authors: Miller
authors: Department of Biology and Microbiology, South Dakota State University, Brookings, SD57007, USA. jai.rohila@sdstate.edu.
authors: Jai S
authors: JS
authors: Rohila
authors: Department of Biology and Microbiology, South Dakota State University, Brookings, SD57007, USA. senthil.subramanian@sdstate.edu.
authors: Senthil
authors: S
authors: Subramanian
authors: School of Life Sciences, University of Nevada, Las Vegas, 89154, USA. jeffery.shen@unlv.edu.
authors: Qingxi J
authors: QJ
authors: Shen
authors: INRA, UMR 1347 Agroécologie, 17 rue Sully, BP 86510, 21065, Dijon, CEDEX, France. dmorandi@dijon.inra.fr.
authors: Dominique
authors: D
authors: Morandi
authors: Department of Biology and Microbiology, South Dakota State University, Brookings, SD57007, USA. Heike.Bucking@sdstate.edu.
authors: Heike
authors: H
authors: Bücking
authors: Department of Biological Sciences, University of North Texas, Denton, TX, 76203, USA. Vladimir.Shulaev@unt.edu.
authors: Vladimir
authors: V
authors: Shulaev
authors: Texas A&M AgriLife Research and Extension Center, Dallas, TX, 75252, USA. wrkypaul1@gmail.com.|Current address, 22nd Century Group Inc., 9530 Main Street Clarence, New York, 14031, USA. wrkypaul1@gmail.com.
authors: Paul J
authors: PJ
authors: Rushton
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics; D020816:Amino Acid Motifs; D016000:Cluster Analysis; D017124:Conserved Sequence; D003375:Coumestrol / Q000378:metabolism; D055864:Droughts; D020869:Gene Expression Profiling; D055442:Metabolome; D055432:Metabolomics / Q000379:methods; D005810:Multigene Family; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D054046:Plant Stomata / Q000235:genetics / Q000378:metabolism; D056510:Position-Specific Scoring Matrices; D011401:Promoter Regions, Genetic; D020543:Proteome; D013025:Glycine max / Q000502:physiology*; D013312:Stress, Physiological / Q000235:genetics; D059467:Transcriptome
chemical_list: D010940:Plant Proteins; D020543:Proteome; D003375:Coumestrol