Expression patterns of novel genes encoding homeodomain leucine-zipper proteins in Arabidopsis thaliana

Abstract

A recently discovered class of genes in Arabidopsis thaliana encode putative transcription factors which contain a homeodomain closely linked to a leucine zipper motif. We have previously reported on the cloning and cDNA sequence of one gene of this class, Athb-3. In this article we show this gene to be expressed predominantly in the cortex of the root and the stem. Using the Athb-3 clone as a probe we have isolated cDNA clones corresponding to three novel homeodomain-leucine zipper proteins. These clones, Athb-5, Athb-6 and Athb-7, hybridized to transcripts that were relatively abundant in the leaf, but also present in other vegetative organs, as well as in the flower. Only weak hybridization was observed to seed pod samples. These observations indicate that these Athb genes have major functions in the mature plant, and therefore, in contrast to homeobox genes in other eukaryotes and to the kn-1 gene in maize, are unlikely to function in the primary control of developmental processes during embryogenesis or organogenesis. The deduced amino acid sequences of Athb-5, Athb-6 and Athb-7 are highly similar to the previously isolated Athb-1, Athb-2 and Athb-3 in the homeodomain and leucine-zipper parts of the proteins, whereas the similarities to homeodomain proteins from other eukaryotes are limited. The Athb proteins thus constitute a new and well defined class of homeodomain proteins, apparently unique to plants.

Environmental Regulation of Lateral Root Emergence inMedicago truncatulaRequires the HD-Zip I Transcription Factor HB1

“…However, one of the closest Arabidopsis Class II genes involved in nitrogen metabolism (Rubin et al, 2009), LBD37, contains a CAATAATTG cis-element in the proximal promoter region. As Arabidopsis HB7 and 12 are strongly induced by ABA in roots (Soderman et al, 1994;Olsson et al, 2004;Ariel et al, 2007), the repression of auxin-responsive genes in response to environmental cues may be driven by a conserved regulatory pathway. ChIP-PCR assays reliably monitor direct interactions of TFs with their targets and have unraveled regulatory networks acting in nodule organogenesis in the legume (Hirsch et al, 2009).…”

Isolation and characterization of two homeodomain leucine zipper genes from the dioecious plant Silene latifolia.

“…The HD-Zip domain of SlHDL1 shows a high degree of similarity with the HD-Zip domains of Athb5 from Arabidopsis thaliana (89%), Hfi22 from Nicotiana tabacum (92%), and GmHDL56 from soybean (93%) (Soderman et al, 1999;Tang et al, 2001;Desvoyes et al, 2002;Rubeti et al, 1991). On the other hand, the HD-Zip domain of SlHDL2 belongs to HD-Zip class II based on its similarity with HAT2 and HAT4 from Arabidopsis thaliana (94% and 93%, respectively) and PHZ2 from Pimpinella brachycarpa (95%) (Soderman et al, 1994;Deng et al, 2002;Schena et al, 1993). To determine the evolutionary relatedness of SlHDL1 and SlHDL2 to HD-Zips isolated from other species, the neighbor-joining method (NJ) was used to generate a gene tree based on amino acid sequence homology of the HD-Zip region of isolated genes to those of HD-Zip proteins (Fig.…”

A physical map of chromosome 2 of Arabidopsis thaliana.

“…); genomic clones in pUC119 (R. Whittier, Mitsui Plant Biotechnology Research Institute, Tsukuba, Japan); AGL3 (Ma et al 1991); Athb7 (Soderman et al 1994); B68 (E. Wisman, Max-Planck-Institut f~r Zuechtungsforschung, Cologne, Germany); GPA1 (Ma et al 1990); 05841 and O802F (C. Lister, The John Innes Centre, Norwich, UK); pCIT4241 and pCITdlO0 (ABRC, Ohio State University, Columbus, OH); ABL3 (Long et al 1993); PR1 (Ulknes et al 1992); TEn5 (formerly PR21) (Aarts et al 1995); pTHY-1 (Lazar et al 1993); pSKFI09 0. Polacco, University of Missouri, Columbia); spl3 (G. Cardon and P. Huijser, Max-Planck-Institut f~ir Zuechtungsforschung, Cologne, Germany); pATC4 (Nairn et al 1988); AGL20 (formerly SG5) (S. Gold and M. Yanofsky, unpubl.…”