foley et al

foley et al - Plant Llolecular Srblqgr'3ll 6t-695 1996 O...

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Plant Llolecular Srblqgr'3ll: 6t?-695. 1996. O 1996 Khtrrlr Aca&mic Publislvrs. Prined in Eclgiun. 6t7 A novel phloem-specific gene'is expressed preferentially in aerial portions of Yicia faba Rhonda C. Foley, Zhi1\dei Liting and'Karam B. Singhl Department of Motecular, Celt and Developmcntal Biolog,, University of California Los Angeles, 405 Hilgard Avenue, Ins Angeles, CA 90095-1606. USA (a aurtor for conespondence) '' Rcceivcd ? August t95. acccped in reviscd form 23 Ocrobcr 1995 Ke-r* words: histidine-rich motif, phloem-specific gae, Vicia faba, bean, Veinl Abstract We have isolated a gene from bean (Vicia faba L.\,called Vein l, that encodes a novel protein. The Vein I cDNA was isolated as a result of a differentid screen for genes that are expressed in leaves but not in the most common cell typg the mesophyll cell. Northern blot analysis revealed that Veinl transcripts are difrerentially expressed in the plant with expression in leaves, stems and scpds but not in petds, mesophyll cells or roots. /n n'ru hybridization studies of stem and leaf sections indicate that the expression of Veinl is locelizecl to tlie phloem tissue. Intcrestingly, Veinl was differentially expressed in stem tis- sue with the highest expiession in the oldest internodes. The deduced Veinl protein sequence does not share homology with any knowu protein sequences. The 17 kDa Veinl protein is highly hydrophilic and contains a hisridine-rich motif, where six out of seven anrino acids are histidincs. The function of Vein I is unknown, although the expression patterns suggests that it.may play a role in mature phloem tissue in the aerial parts of the plant. Introduction A number of genes that have been found to be differentially expressed in leafare expressed spe- cificallf in the vascular tissue. The vascular tissue is continuous throughout the plant and plays pri- mar.v roles in the transport of water and solutes as well as providing structural suppon. The iden- tification and characterization of genes expressed specificdly in vascular tissue should lead to a better understanding of the mechanisms underly- ing vascular function. A number of the genes ex- pressed specifically or preferentially in the vascu- lar tissue encode proteins that are compon€nts of the plant cell wall (refer to the summary table in Il8f and references within). These cell wall struc- tural proteins have been classified into a number of groups that include the h.vdroxyproline-rich glycoproteins (HRGP), the proline rich proteins (PRP) and the glycine-rich proreins (GRP). tn a number of cases the expression of these cell wall proteins has been localized to specific cell types The nuclcotidc squence data reponcd will appcar in rhc EMBL. GcnBank and DDBJ Nucleotide Sequclce Darabases under rhc accession numbcr Xt9207.
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688 in the vascular dssue. HRGPs have been local- ized to vascular meristematic cells as well as xylem and phloem 6bers [20,25,261. The PRPs and GRPs have been localized to the xylem and phloem [25. 26. 23, 16]. In addition, a novel t1'rosind- and lysine-rich protdih ha3 treri locel-
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foley et al - Plant Llolecular Srblqgr'3ll 6t-695 1996 O...

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