title: Proteomics and metabolomics analyses reveal the cucurbit sieve tube system as a complex metabolic space.
abstract: The plant vascular system, and specifically the phloem, plays a pivotal role in allocation of fixed carbon to developing sink organs. Although the processes involved in loading and unloading of sugars and amino acids are well characterized, little information is available regarding the nature of other metabolites in the sieve tube system (STS) at specific sites along the pathway. Here, we elucidate spatial features of metabolite composition mapped with phloem enzymes along the cucurbit STS. Phloem sap (PS) was collected from the loading (source), unloading (apical sink region) and shoot-root junction regions of cucumber, watermelon and pumpkin. Our PS analyses revealed significant differences in the metabolic and proteomic profiles both along the source-sink pathway and between the STSs of these three cucurbits. In addition, metabolite profiles established for PS and vascular tissue indicated the presence of distinct compositions, consistent with the operation of the STS as a unique symplasmic domain. In this regard, at various locations along the STS we could map metabolites and their related enzymes to specific metabolic pathways. These findings are discussed with regard to the function of the STS as a unique and highly complex metabolic space within the plant vascular system.
authors.affiliation: Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA.|Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, SJTU-University of Adelaide Joint Centre for Agriculture and Health, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Chaoyang
authors.initials: C
authors.lastname: Hu
authors.affiliation: Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA.
authors.forename: Byung-Kook
authors.initials: BK
authors.lastname: Ham
authors.affiliation: Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA.|Plant Biotechnology Department, National Research Center, El-Behouth St, Dokki, Giza, 12622, Egypt.
authors.forename: Hattem M
authors.initials: HM
authors.lastname: El-Shabrawi
authors.affiliation: Metabolon Inc., Durham, NC, 27713, USA.
authors.forename: Danny
authors.initials: D
authors.lastname: Alexander
authors.affiliation: Joint International Research Laboratory of Metabolic and Developmental Sciences, School of Life Sciences and Biotechnology, SJTU-University of Adelaide Joint Centre for Agriculture and Health, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Dabing
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Metabolon Inc., Durham, NC, 27713, USA.
authors.forename: John
authors.initials: J
authors.lastname: Ryals
authors.affiliation: Department of Plant Biology, College of Biological Sciences, University of California, Davis, CA, 95616, USA. wjlucas@ucdavis.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Lucas
mesh_terms: D028462:Cucumis / Q000378:metabolism*; D018553:Cucumis sativus / Q000378:metabolism; D055432:Metabolomics / Q000379:methods*; D052585:Phloem / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D040901:Proteomics / Q000379:methods*
chemical_list: D010940:Plant Proteins
keywords: Citrullus lanatus; Cucumis sativus; Cucurbita maxima; Cucurbits; metabolic compartment; metabolomics; phloem sap; proteomics; sieve tube system; source-sink pathway