SKS6, a multicopper oxidase-like gene, participates in cotyledon vascular patterning during Arabidopsis thaliana development

Abstract

SKU5-Similar 6 (SKS6) is a one of a large gene family of 19 members in Arabidopsis thaliana (L.) Heynh that encode multicopper oxidase-like proteins that are related to ferroxidases, ascorbate oxidases and laccases. Only one member of the family has been previously studied; Skewed5 (SKU5) is involved in the control of root growth. The encoded SKS6 protein, like SKU5 appears to lack a functional copper-binding site and is most closely related to Bp10 from Brassica napus and Ntp303 from Nicotiana tobacum. The SKS6 promoter contains many putative regulatory sites and differential expression of an SKS6::GUS reporter gene revealed selective induction in several seedling tissues including guard cells, root cortex cells, and leaf margin hydathodes. It was also expressed later in flower development in flower primordia, ovules, and the abscission zones of seeds and siliques. Furthermore, SKS6 was upregulated in roots in response to treatment of seedlings with the hormones abscisic acid, indole-3 acetic acid, 2,4-dichlorophenoxyacetic acid and aminocyclopropane-1-carboxylate. A loss-of function sks6-1 T-DNA insertion allele revealed that cotyledon vascular patterning is affected in the mutant, suggesting a role for the protein in metabolism of nutrients or hormones in the hydathodes, the sites of auxin synthesis and chemical recycling.

AUXIN BINDING PROTEIN1: The Outsider

“…in cotyledon vasculature (Jacobs and Roe, 2005), which might also be found also in ABP1 downregulated lines (unreferenced comment in Tromas et al, 2010). This evidence, although weak and circumstantial, deserves closer inspection.…”

A Novel Approach to Dissect the Abscission Process in Arabidopsis

“…The sequences of these proteins share similarities to ascorbate oxidases and laccases, two families of multicopper oxidases that integrate four copper ions into three regions (types 1, 2, and 3); however, the amino acid domains where the copper ions bind are conserved in both of these two families, but in the genes of the SKS family, regions type 1 and 3 are missing and motif 2 is not intact, suggesting that SKS genes are monocopper oxidases rather than pectin esterases and that their specificity remains to be elucidated (Sedbrook et al, 2002;Jacobs and Roe, 2005).…”

Comparison of two ecotypes of the metal hyperaccumulator Thlaspi caerulescens (J. & C. PRESL) at the transcriptional level

“…Multicopper binding proteins belong to a large family (SKS), and it is speculated that SKS6 gene is expressed in response to environmental stimuli (Jacobs and Roe 2005). The SKU5 gene was mainly expressed in the expanding root tissue of Arabidopsis, and the protein was shown to be localised to the plasma membrane and cell wall (Sedbrook et al 2002).…”