Characterization of cis-acting sequences regulating root-specific gene expression in tobacco.

Abstract

The expression of the tobacco root-specific gene TobRB7 was characterized. Gel blot hybridizations to RNA isolated from various tobacco tissues demonstrated that steady-state TobRB7 mRNA is not detected in expanded leaf, stem, or shoot apex tissue. To determine the spatial pattern of expression, in situ hybridization to root sections revealed that TobRB7 expression is localized to root meristem and immature central cylinder regions. The 5' flanking region of the gene was studied with respect to its ability to direct root-specific expression. Deletions of 5' flanking sequence were fused to the /3-glucuronidase (GUS) reporter gene and transformed into tobacco. Our data demonstrated that sequences 636 base pairs from the site of transcription initiation are sufficient to direct the root-specific GUS expression in transgenic tobacco, whereas sequences 299 base pairs from the site of transcription initiation fail to direct root-specific expression. A negative regulatory element was apparent between 813 base pairs and 636 base pairs 5' of the transcription initiation site. Histochemical localization of GUS activity in transgenic plants was consistent with in situ hybridization results: GUS activity was localized to the root meristem and central cylinder regions. GUS activity appeared 2 days post-germination in the primary root meristem. In lateral roots, GUS activity was detected from the time of initiation.

Aquaporin function, structure, and expression: are there more surprises to surface in water relations?

“…Consistent observations locate both PIP and TIP expression in the vascular tissue and surrounding cells, including early developmental stages (Yamamoto et al 1991;Kaldenho et al 1995;Yamada et al 1995;Daniels et al 1996). In situ hybridization experiments reveal the highest PIP mRNA levels in the region of Arabidopsis vasculature (Fig.…”

Proper gibberellin localization in vascular tissue is required to regulate adventitious root development in tobacco

“…In this study, PtGA20ox and PtGA2ox1 were expressed under the control of two well-studied promoters, namely LMX5 and TobRB7 , respectively, leading to expression on the xylem side of the cambial zone in the stem (Bjorklund et al ., 2007) and the meristem and central cylinder regions in the root (Yamamoto et al ., 1991). The results show that the precise tissue localization of GAs regulates adventitious root initiation and elongation in tobacco.…”

Expression and distribution of a vacuolar aquaporin in young and mature leaf tissues of Brassica napus in relation to water fluxes

“…Dierent observations indicate that dierential expression of aquaporins regulates water¯uxes in plants. Yamamoto et al (1991) showed that TobRB7, a putative plasma-membrane water channel of tobacco, is highly expressed in the meristem and the immature central cylinder of roots. The tonoplast aquaporin c-tonoplast intrinsic protein (c-TIP; Ludevid et al 1992) and AthH2/AtPIP1b (Kaldenho et al 1995), a plasma-membrane aquaporin, are both expressed in young, developing tissue.…”