Ubiquitous presence of β-glucuronidase (GUS) in plants and its regulation in some model plants

Abstract

The enzyme beta-glucuronidase (GUS) is well characterized in animals and microbes. However, this enzyme is not well studied in plants and is widely assumed to be absent in them. In this study we document the ubiquitous presence of GUS in the model plants Arabidopsis thaliana, Oryza sativa, Nicotiana tabacum and Zea mays and record its expression pattern. The pH of the assay buffer was found to be critical with pH 4.0 being optimum for detection in all the species. GUS in plants appears to be associated with growth. In general, younger regions of the organs showed more GUS activity than the older and more mature tissues. In Brassica juncea roots stained for GUS, intense blue color could be seen in the trichoblast cells and the growing root hair cells as compared to the non-root hair forming epidermal cells or the fully elongated root hairs. Cotton fibers showed high GUS activity during the initial phase of elongation while the seed coat, from which the fibers formed, did not stain for GUS activity. The activity in the fibers disappeared after they were fully elongated. The level of GUS activity increased 2.58 folds in leaf tissues of N. tabacum when cultured in MS medium supplemented with 6-benzylaminopurine, while gibberellic acid enhanced GUS activity 2.9 folds in the inter-nodal regions of rice in 12-h treatment. In addition, elongation of stem, root and root hairs in tobacco seedlings was strongly inhibited by the specific inhibitor of GUS, saccharo-1-4-lactone in a reversible manner. Taken together, these evidences suggest a probable association of plant GUS in cell growth.

Endogenous GUS-like activity in Capsicum chinense Jacq.

“…The gene uidA codes for β-glucuronidase which is utilized as a reporter in plant genetic transformation because it is generally believed that higher plants do not show GUS-like endogenous activity (Jefferson, 1987;Martin et al 1991;Sudan et al 2006). However, several studies have demonstrated that some plant species show endogenous GUS-like activity in vegetative tissues as well as reproductive organs (Cervera, 2005;Sudan et al 2006).…”

“…However, several studies have demonstrated that some plant species show endogenous GUS-like activity in vegetative tissues as well as reproductive organs (Cervera, 2005;Sudan et al 2006). …”

Transient genetic transformation of embryogenic callus of Cocos nucifera

“…In different species optimal endogenous GUS-like activity has been reported between pH 4 and pH 6 (Hodal et al 1992), whereas it is histochemically undetectable at pH 7.0 or higher (Alwen et al 1992;Hodal et al 1992;Sudan et al 2006;Solís-Ramos et al 2010a). In contrast, the pH of E. coli-derived GUS has optimum activity at pH 7.0 (Jefferson 1987).…”

“…In contrast, the pH of E. coli-derived GUS has optimum activity at pH 7.0 (Jefferson 1987). Therefore, assaying at this pH for transformation-associated GUS activity, could be a means to discriminate the E. coli-derived GUS from endogenous GUS-like activity (Sudan et al 2006). On the other hand, Kosugi et al (1990) proposed that the use of methanol in GUS buffer eliminated endogenous GUS-like activity, while having no effect or even enhancing the activity of the introduced gusA gene.…”

Tissue culture independent transformation of the forage crop sunnhemp (Crotalaria juncea L.): an easy method towards generation of transgenics

“…Since it has been reported that many legumes exhibit endogenous GUS like activity (Sudan et al 2006), we chose to avoid the use of GUS gene as marker. Instead the FMDV ID gene of the two serotypes "O" and "A 22 " which encodes for major antigenic protein and induces immune response in animals (Meloen and Barteling 1986) was linked together and its expression was used to assess the transformation efficiency.…”