Cell Specific, Cross-Species Expression of Myrosinases in Brassica Napus, Arabidopsis Thaliana and Nicotiana Tabacum

Abstract

A prototypical characteristic of the Brassicaceae is the presence of the myrosinase-glucosinolate system. Myrosinase, the only known S-glycosidase in plants, degrades glucosinolates, thereby initiating the formation of isothiocyanates, nitriles and other reactive products with biological activities. We have used myrosinase gene promoters from Brassica napus and Arabidopsis thaliana fused to the beta -glucuronidase (GUS) reporter gene and introduced into Arabidopsis thaliana, Brassica napus and/or Nicotiana tabacum plants to compare and determine the cell types expressing the myrosinase genes and the GUS expression regulated by these promoters. The A. thaliana TGG1 promoter directs expression to guard cells and phloem myrosin cell idioblasts of transgenic A. thaliana plants. Expression from the same promoter construct in transgenic tobacco plants lacking the myrosinase enzyme system also directs expression to guard cells. The B. napus Myr1.Bn1 promoter directs a cell specific expression to idioblast myrosin cells of immature and mature seeds and myrosin cells of phloem of B. napus. In A. thaliana the B. napus promoter directs expression to guard cells similar to the expression pattern of TGG1. The Myr1.Bn1 signal peptide targets the gene product to the reticular myrosin grains of myrosin cells. Our results indicate that myrosinase gene promoters from Brassicaceae direct cell, organ and developmental specific expression in B. napus, A. thaliana and N. tabacum.

Nonuniform distribution of glucosinolates in Arabidopsis thaliana leaves has important consequences for plant defense

“…In contrast to glucosinolates, much more is known about the cell-and organ-level localization of myrosinase. This glucosinolate-activating enzyme is known from all plant organs (4), and in A. thaliana is reported from the phloem parenchyma as well as guard cells (34,35). Unlike glucosinolates, we found myrosinase activity to be uniformly distributed among the different sectors of the leaf examined.…”

Disruption of Adenosine-5′-Phosphosulfate Kinase inArabidopsisReduces Levels of Sulfated Secondary Metabolites

“…This is believed to be due to a higher level being present at the parts of the leaf most vulnerable to damage by insects: the main vein, which needs to be protected from damage to prevent the disruption of the movement of nutrients and water through the leaf, and the edges of the leaf, which are most accessible to chewing insects. Myrosinase has been shown to be localized specifically in myrosin cells of the phloem parenchyma in Arabidopsis (André asson et al, 2001) and in guard cells (André asson et al, 2001;Thangstad et al, 2004). Koroleva et al (2000) also demonstrated a high amount of GLs in specific S-cells in flower stalks associated with vasculature.…”

Defence mechanisms of Brassicaceae: implications for plant-insect interactions and potential for integrated pest management. A review

“…The myrosin cells can be easily distinguished from their neighbouring cells by light, electron and confocal microscopic observations (Bones and Iversen, 1985;Thangstad et al, 1990Thangstad et al, , 1991Bones et al, 1991;Thangstad et al, 2004;Kissen et al, 2009). The myrosin cells contain less lipids, a high content of endoplasmic reticulum and harbour smooth-looking protein bodies referred to as myrosin grains (Bones and Iversen, 1985;Thangstad et al, 1991).…”

“…Myrosin cells exist as scattered cells in stems, leaves, seeds, seedlings, petioles and roots. Brassica plants contain the enzyme myrosinase (β-thioglucoside glucohydrolase, thioglucosidase, EC 3.2.3.147 (formerly EC 3.2.3.1) (Bones and Slupphaug, 1989;Bones, 1990;Bones andRossiter, 1996, 2006), which is thought to be exclusively present in myrosin cells (Thangstad et al, 1990Bones et al, 1991;Höglund et al, 1991;Husebye et al, 2002;Thangstad et al, 2004;Kissen et al, 2009). In brassicas, myrosinases can be divided into three different gene families; the MA, MB and MC families (Xue et al, 1992;Chadchawan et al, 1993;Lenman et al, 1993;Thangstad et al, 1993;Falk et al, 1995).…”