Plant Science 253 (2016) 206–214 Contents lists available at ScienceDirect Plant Science j ourna l ho me pa g e: www.elsevier.com/locate/plantsci The cell wall DUF642 At2g41800 (TEB) protein is involved in hypocotyl cell elongation Alexis Salazar-Iribe a , Lourdes Teresa Agredano-Moreno b , Esther Zú˜ niga-Sánchez a , Luis Felipe Jiménez-Garcia b , Dr. Alicia Gamboa-deBuen a,∗ a Instituto de Ecología, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP. 04510, México DF, Mexico b Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, CP. 04510, México DF, Mexico a r t i c l e i n f o Article history: Received 23 May 2016 Received in revised form 10 October 2016 Accepted 12 October 2016 Available online 13 October 2016 Keywords: Arabidopsis thaliana Cell wall DUF642 proteins Hypocotyls Pectin a b s t r a c t In plants, the cell wall is a complex and dynamic structure comprising high molecular weight carbohy- drates and proteins. The cell wall plays an important role in several stages of the plant life cycle, including cell division, elongation and differentiation. The DUF642 family of cell wall proteins is highly conserved in spermatophytes and might be involved in pectin structural modifications. Particularly, At2g41800 is one of the most highly induced genes during the M/G1 phases of the cell cycle, and the protein encodes by this gene has been detected in cell wall proteomes of cell suspension cultures. In the present study, the expression of At2g41800 (TEB) was confirmed in primary and lateral roots, stigmatic papillae and hypocotyls. Subcellular localization studies showed that TEB is located in the cell wall. The root length and lateral root density were not affected in either of the two teb mutants studied, but the length of the hypocotyls from seedlings grown under light and dark conditions was increased. Immunogold labelling studies using JIM5 antibodies on sections of hypocotyl epidermal cells showed an important reduction of gold particles in teb mutants. The results suggested that TEB is involved in hypocotyl elongation. © 2016 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Cell growth in plants is highly regulated according to the compo- sition and properties of the cell wall. Cell division and cell expansion processes require changes in the cell wall composition as well as the deposition of new material [1]. The plant cell wall is a dynamic structure comprising high molecular weight carbohydrates and proteins with known and unknown functions. The relevance of these protein interactions and functional studies of putative cell wall proteins of unknown function has recently been highlighted [2]. The DUF642 family is a highly conserved family of cell wall- related proteins specific to spermatophytes. The phylogenetic tree Abbreviations: AtPME3, Arabidopsis thaliana pectin methyl esterase 3; BDX, BIIDXI (At4g32460); BSA, bovine serum albumin; CIM, callus induction medium; DIC, differential interference contrast; DMSO, dimethyl sulfoxide; DUF, domains of unknown function; DGR, DUF642 L-GalL responsive gene; GFP, green fluores- cence protein; HG, homogalacturonan; HU, hydroxyurea; MS, Murashige and Skoog medium; NGS, normal goat serum; PLA, pectate lyase; PME, pectin methyl esterase; PG, polygalacturonase; RT-PCR, reverse transcription-PCR; TEB, (At2g41800); TBS, tris-buffered saline. ∗ Corresponding author. E-mail address: agamboa@ecologia.unam.mx (A. Gamboa-deBuen). of this family retrieved 4 clades: clade A, which includes cell wall proteins with a signal peptide and a DUF642 domain, and clades B, C, and D, which include DUF642 proteins localized to the membrane based on the presence of a GPI anchor site. The DUF642 domain has structural similarities to carbohydrate bind- ing domains. The At3g08030 protein, present in cell wall proteomes from different tissues, interacts in vitro with cellulose and hemicel- lulose [3]. Recent studies also suggested that the DUF642 family of proteins could be involved in pectin structural modifications. Pro- teins encoded by BIIDXI (BDX, At4g32460) and At5g11420 interact in vitro with AtPME3, a pectin methyl esterase (PME) from Arabidop- sis thaliana involved in different plant developmental processes [4]. BDX positively regulates PME activation during Arabidopsis seed germination and siliqua development. Germination param- eters are improved in the seeds of plants overexpressing BDX, and a positive correlation was observed between the increase in testa rupture velocity and PME activity. A reduction in total PME activ- ity was detected in bdx heterozygous mutants, in which siliques were short with few seeds [5]. An increase in PME activity was also detected in the leaves of Vitis quinquangularis plants overexpressing VqDUF642, which is involved in berry development and pathogen resistance [6]. http://dx.doi.org/10.1016/j.plantsci.2016.10.007 0168-9452/© 2016 Elsevier Ireland Ltd. All rights reserved.