RESUMEN
Cold stress on plants induces changes in the transcription of cold response genes. A cDNA clone encoding C2H2-type zinc finger protein, SCOF-1, was isolated from soybean. The transcription of SCOF-1 is specifically induced by low temperature and abscisic acid (ABA) but not by dehydration or high salinity. Constitutive overexpression of SCOF-1 induced cold-regulated (COR) gene expression and enhanced cold tolerance of non-acclimated transgenic Arabidopsis and tobacco plants. SCOF-1 localized to the nucleus but did not bind directly to either C-repeat/dehydration (CRT/DRE) or ABA responsive element (ABRE), cis-acting DNA regulatory elements present in COR gene promoters. However, SCOF-1 greatly enhanced the DNA binding activity of SGBF-1, a soybean G-box binding bZIP transcription factor, to ABRE in vitro. SCOF-1 also interacted with SGBF-1 in a yeast two-hybrid system. The SGBF-1 transactivated the beta-glucuronidase reporter gene driven by the ABRE element in Arabidopsis leaf protoplasts. Furthermore, the SCOF-1 enhanced ABRE-dependent gene expression mediated by SGBF-1. These results suggest that SCOF-1 may function as a positive regulator of COR gene expression mediated by ABRE via protein-protein interaction, which in turn enhances cold tolerance of plants.
Asunto(s)
Adaptación Fisiológica/genética , Frío , Glycine max/genética , Proteínas de Choque Térmico/fisiología , Proteínas de Plantas , Plantas Modificadas Genéticamente/fisiología , Factores de Transcripción/fisiología , Dedos de Zinc , Ácido Abscísico/farmacología , Secuencia de Aminoácidos , Secuencia de Bases , Núcleo Celular/metabolismo , Cartilla de ADN , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes Reporteros , Glucuronidasa/genética , Proteínas de Choque Térmico/química , Proteínas de Choque Térmico/genética , Datos de Secuencia Molecular , Plantas Modificadas Genéticamente/genética , Homología de Secuencia de Aminoácido , Factores de Transcripción/química , Factores de Transcripción/genética , Activación TranscripcionalRESUMEN
Very limited information is available on the role of phosphatidylinositol 3-phosphate (PI[3]P) in vesicle trafficking in plant cells. To investigate the role of PI(3)P during the vesicle trafficking in plant cells, we exploited the PI(3)P-specific binding property of the endosome binding domain (EBD) (amino acids 1257 to 1411) of human early endosome antigen 1, which is involved in endosome fusion. When expressed transiently in Arabidopsis protoplasts, a green fluorescent protein (GFP):EBD fusion protein exhibited PI(3)P-dependent localization to various compartments--such as the trans-Golgi network, the prevacuolar compartment, the tonoplasts, and the vesicles in the vacuolar lumen--that varied with time. The internalized GFP:EBD eventually disappeared from the lumen. Deletion experiments revealed that the PI(3)P-dependent localization required the Rab5 binding motif in addition to the zinc finger motif. Overexpression of GFP:EBD inhibited vacuolar trafficking of sporamin but not trafficking of H(+)-ATPase to the plasma membrane. On the basis of these results, we propose that the trafficking of GFP:EBD reflects that of PI(3)P and that PI(3)P synthesized at the trans-Golgi network is transported to the vacuole through the prevacuolar compartment for degradation in plant cells.
Asunto(s)
Arabidopsis/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Vacuolas/metabolismo , Red trans-Golgi/metabolismo , Arabidopsis/genética , Secuencia de Bases , Sitios de Unión , Transporte Biológico Activo , ADN Recombinante/genética , Endosomas/metabolismo , Fusión de Membrana , Proteínas de la Membrana/química , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Modelos Biológicos , Plantas Modificadas Genéticamente , Estructura Terciaria de Proteína , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas de Transporte VesicularRESUMEN
Two separate nuclear binding activities (B1 and B2) in the soybean apical hypocotyl have been identified that interact with a palindromic C-box sequence (TGACGTCA) and which are developmentally regulated in an inverse manner. The bZIP factors responsible for these two binding activities, B1 and B2, were isolated from a cDNA library and designated STGA1 and STFs (STF1 and STF2), respectively. Sequence analysis shows that the STFs contain both a zinc-finger domain and a bZIP domain. The two zinc finger sequences of Cys4-Cys4 are most related to the RING zinc-finger motif carrying a Cys3-His-Cys4. In addition the bZIP domain of STFs is highly homologous to the HY5 protein of Arabidopsis. DNA binding studies revealed that STF1 binding to the TGACGT sequence requires distinct flanking sequences. Furthermore, STF1 binds to the Hex sequence as a heterodimer with G-box binding factors (GBFs), a feature not observed with STGA1. Since STF1 expression is most prevalent in apical and elongating hypocotyls, it is proposed that STF1 may be a transcription factor involved in the process of hypocotyl elongation.
