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Interaction of brassinosteroids and cytokinin in modulating light mediated signaling in Arabidopsis
Hwang, Indeok,Paudyal, Dilli P.,Cheong, Hyeonsook The Basic Science Institute Chosun University 2008 조선자연과학논문집 Vol.1 No.1
Brassinosteroids (BRs) are a special class of plant steroid hormones that are essential for normal growth and development. Part of confusion is whether BRs are unique to plants, because they have overlapping physiological roles with other better-studied hormones and with physiological responses caused by light. In systems designed to assay for cytokinins, the effects of BRs vary. We measured hypocotyl length for testing the ability of brassinolide (BL) to rescue double mutant between det2 and the photoreceptor null mutant phytochrome B (phyB). PHYB involved in controlling hypocotyl elongation in increased concentration of BL whereas phyBdet2 double mutant just partially rescue to phyB in white and red light indicated the involvement of BRs in PHYB regulated cell elongation. BRs regulated hypocotyl growth was delayed by BAP, a cytokinin treatment but inhibitory effects of BAPs on hypocotyl growth was slightly recovered by BL. The result indicated that the mode of action of BR and cytokinin is independent or sequential in the downstream light-regulated response control on hypocotyl elongation and also light modulated the action of BR and cytokinin in some extent.
Indeok Hwang,Ill-Sup Nou 한국육종학회 2014 한국육종학회 심포지엄 Vol.2014 No.07
Plant bZIP transcription factors play crucial roles in biological processes. In this study, 136 putative bZIP transcription members were identified in Brassica rapa. The bZIP family can be divided into nine groups according to the specific amino acid rich domain in Brassica rapa. To screen the cold stress responsive BrbZIP genes, we evaluated whether the transcription patterns of the BrbZIP genes were enhanced by cold treatment in the inbred lines, Chiifu and Kenshin, by microarray data analysis and qRT-PCR. The expression level of six genes increased significantly in Kenshin, but these genes were unchanged in Chiffu. Additionally, homo- and hetero-dimerization test between selected bZIP proteins indicated the Bra020735 is a key regulator in cold response. These findings suggest that the six genes that encoded proteins containing N-rich regions might be involved in cold stress response. These results presented herein provide valuable information regarding the molecular basis of the bZIP transcription factors and their potential function in regulation growth and development, particularly in cold stress response.
Hwang, Indeok,Kim, Soo Young,Kim, Cheol Soo,Park, Yoonkyung,Tripathi, Giri Raj,Kim, Seong-Ki,Cheong, Hyeonsook Springer Netherlands 2010 Plant Molecular Biology Vol.73 No.6
<P>Shoot branching and growth are controlled by phytohormones such as auxin and other components in <I>Arabidopsis</I>. We identified a mutant (<I>igi1</I>) showing decreased height and bunchy branching patterns. The phenotypes reverted to the wild type in response to RNA interference with the <I>IGI1</I> gene. Histochemical analysis by GUS assay revealed tissue-specific gene expression in the anther and showed that the expression levels of the <I>IGI1</I> gene in apical parts, including flowers, were higher than in other parts of the plants. The auxin biosynthesis component gene, <I>CYP79B2</I>, was up-regulated in <I>igi1</I> mutants and the <I>IGI1</I> gene was down-regulated by IAA treatment. These results indicated that there is an interplay regulation between IGI1 and phytohormone auxin. Moreover, the expression of the auxin-related shoot branching regulation genes, <I>MAX3</I> and <I>MAX4</I>, was down-regulated in <I>igi1</I> mutants. Taken together, these results indicate that the overexpression of the <I>IGI1</I> influenced MAX pathway in the shoot branching regulation.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (doi:10.1007/s11103-010-9645-0) contains supplementary material, which is available to authorized users.</P>
Loss of Function in GIGANTEA Gene is Involved in Brassinosteroid Signaling
Hwang, Indeok,Park, Jaeyoung,Lee, Beomgi,Cheong, Hyeonsook The Basic Science Institute Chosun University 2011 조선자연과학논문집 Vol.4 No.2
Brassinosteroids (BRs) are plant steroid hormones that play essential roles in growth and development. Mutations in BR-signaling pathways cause defective in growth and development like dwarfism, male sterility, abnormal vascular development and photomorphogenesis. Transition from vegetative to reproductive growth is a critical phase change in the development of a flowering plant. In a screen of activation-tagged Arabidopsis, we identified a mutant named abz126 that displayed longer hypocotyls when grown in the dark on MS media containing brassinazole (Brz), an inhibitor of BRs biosynthesis. We have cloned the mutant locus using adapter ligation PCR walking and identified that a single T-DNA had been integrated into the ninth exon of the GIGANTEA (GI) gene, involved in controling flowering time. This insertion resulted in loss-of-function of the GI gene and caused the following phenotypes: long petioles, tall plant height, many rosette leaves and late flowering. RT-PCR assays on abz126 mutant showed that the T-DNA insertion in GIGANTEA led to the loss of mRNA expression of the GI gene. In the hormone dose response assay, abz126 mutant showed: 1) an insensitivity to paclobutrazole (PAC), 2) an altered response with 6-benzylaminopurine (BAP) and 3) insensitive to Brassinolide (BL). Based on these results, we propose that the late flowering and tall phenotypes displayed by the abz126 mutant are caused by a loss-of-function of the GI gene associated with brassinosteroid hormone signaling.
Loss of Function in GIGANTEA Gene is Involved in Brassinosteroid Signaling
Indeok Hwang, Jaeyoung Park, Beomgi Lee, Hyeonsook Cheong 조선대학교 기초과학연구원 2011 조선자연과학논문집 Vol.4 No.2
Brassinosteroids (BRs) are plant steroid hormones that play essential roles in growth and development. Mutations in BR-signaling pathways cause defective in growth and development like dwarfism, male sterility, abnormal vascular development and photomorphogenesis. Transition from vegetative to reproductive growth is a critical phase change in the development of a flowering plant. In a screen of activation-tagged Arabidopsis, we identified a mutant named abz126 that displayed longer hypocotyls when grown in the dark on MS media containing brassinazole (Brz), an inhibitor of BRs biosynthesis. We have cloned the mutant locus using adapter ligation PCR walking and identified that a single T-DNA had been integrated into the ninth exon of the GIGANTEA (GI) gene, involved in controling flowering time. This insertion resulted in loss-of-function of the GI gene and caused the following phenotypes: long petioles, tall plant height, many rosette leaves and late flowering. RT-PCR assays on abz126 mutant showed that the T-DNA insertion in GIGANTEA led to the loss of mRNA expression of the GI gene. In the hormone dose response assay, abz126 mutant showed: 1) an insensitivity to paclobutrazole (PAC), 2) an altered response with 6-benzylaminopurine (BAP) and 3) insensitive to Brassinolide (BL). Based on these results, we propose that the late flowering and tall phenotypes displayed by the abz126 mutant are caused by a loss-of-function of the GI gene associated with brassinosteroid hormone signaling.