The Expression of an Aquaporin Promoter from Mesembryanthemum crystallinum in Tobacco

Abstract

The promoter region of the MipB gene encoding an aquaporin from Mesembryanthemum crystallinum was isolated and used in a transcriptional fusion to control uidA expression in tobacco. The sequence of the promoter was determined for 2 kb upstream of the translation initiation site. Three start sites were utilized with approximately equal frequency, located 176, 170, and 161 bases, respectively, upstream of the translation initiation site. As judged by analysis of GUS expression, promoter MipB retains its specificity in transgenic tobacco. In germinating seedlings, all cells showed GUS expression of different intensities with the strongest signals in root meristems. In older seedlings, GUS staining was observed in rapidly expanding cells--root and apical meristem, and lateral root primordia. In mature plants, strong GUS activity was located to glandular trichomes, subepidermal cells of the stem and petioles, to cells surrounding vascular tissues as well as in xylem parenchyma cells. In immature floral organs, GUS expression was strong in sepals, petals, stamen, and pistil. The intensity declined as they matured. In general, this promoter was active in rapidly expanding cells and cells with high water flux capacity, especially in the xylem parenchyma.

Expression of Water Channel Proteins in Mesembryanthemum crystallinum

“…Up to the present, few immunological analyses monitored cell specificity of individual MIPs (Yamamoto et al, 1991;Jones and Mullet, 1995;Kaldenhoff et al, 1995;Sarda et al, 1997). Other analyses reported transcript location using in situ hybridization (Yamada et al, 1995;Sarda et al, 1997;Barrieu et al, 1998;Chaumont et al, 1998) or the analysis of Mip-promoter GUS fusions (Yamamoto et al, 1991;Yamada et al, 1997). We have chosen to present immunological data from root and stem analysis because the signature cell types that distinguish the four proteins for which we generated antibodies are most clearly observed in these tissues.…”

“…Mip genes are seed, root, and leaf specific, and are associated with leaf expansion, root tip elongation, or seedling development (Guerrero et al, 1990;Yamamoto et al, 1991;Hö fte et al, 1992;Jones and Mullet, 1995;Fukuhara et al, 1999). Cell specificity has been reported for some Mip genes based on in situ hybridizations or by monitoring Mip-promoter-controlled uidA (␤-glucuronidase [GUS]) activity (Yamamoto et al, 1991;Jones and Mullet, 1995;Kaldenhoff et al, 1995;Yamada et al, 1995Yamada et al, , 1997Barrieu et al, 1998;Chaumont et al, 1998). Studies on Mip expression have indicated regulation by environmental factors such as drought, salinity, or temperature (YamaguchiShinozaki et al, 1992;Jones and Mullet, 1995;Yamada et al, 1995;Maurel, 1997;Johansson et al, 1998).…”

Leaf Development Monitoring and Early Detection of Water Deficiency by Low Field Nuclear Magnetic Resonance Relaxation in Nicotiana tabacum Plants

“…All of these mechanisms can be affected by water stress, a reduction in the water in the leaf and hence in the vacuoles is a known effect of water stress [25] as is an increase in the concentration of soluble compounds [53]. Moreover, the permeability of the tonoplast increases [54,55] or decreases [56,57] depending on the stress and the species.…”

Inhibition of Water Channels by HgCl2 in Intact Wheat Root Cells1

“…The inhibition of L P by HgCl 2 was similar in magnitude to that caused by hypoxia, and the addition of HgCl 2 to hypoxia-treated cells did not result in further inhibition. We compared the L P of intact cells with that predicted from a model of cortical cells incorporating water flow across both the plasma membrane and the tonoplast using measured values of water permeability from isolated membranes, and found that HgCl 2 has other effects in addition to the direct inhibition of water channels.The cloning and functional expression of aquaporins from higher plants (Maurel et al, 1993(Maurel et al, , 1997a Daniels et al, 1994 Daniels et al, , 1996 Kammerloher et al, 1994;Yamada et al, 1997;Weig et al, 1997; Chaumont et al, 1998; Johansson et al, 1998) has indicated that water flow across intact higher plant membranes could be predominantly through aquaporins. The biophysical evidence for this in higher plants has lagged behind the molecular work, but recent studies have shown that biophysical characteristics of water transport are consistent with water flow occurring predominantly through channels in some membranes.…”

“…The cloning and functional expression of aquaporins from higher plants (Maurel et al, 1993(Maurel et al, , 1997a Daniels et al, 1994 Daniels et al, , 1996 Kammerloher et al, 1994;Yamada et al, 1997;Weig et al, 1997; Chaumont et al, 1998; Johansson et al, 1998) has indicated that water flow across intact higher plant membranes could be predominantly through aquaporins. The biophysical evidence for this in higher plants has lagged behind the molecular work, but recent studies have shown that biophysical characteristics of water transport are consistent with water flow occurring predominantly through channels in some membranes.…”