Regulation of shoot development in maize via brassinosteroid signaling

Brassinosteroids (BR) are a class of phytohormones with many important roles in plant growth and development. Compared to other model organisms BR signaling is poorly understood in maize. To study BR signaling\u27s role in maize growth and development we suppressed two members of the BR signaling pathway, BRI1 and BIN2, by RNAi approach. BLAST searches and phylogenetic analyses suggested that there are two BRI1 copies and three BRI1-like genes (BRL) homologs in maize. bri1b, which is located on chr 5, was incomplete in databases, but via subsequent cloning and sequencing was found to be an intact and expressed gene. These two closely related bri1 homologs, named bri1a and bri1b, share 93% amino acid identity and 95% similarity. Suppression of BRI1 homologs lead to dwarf plants with upright, dark green, and thicker leaves. Blade/sheath boundary was disrupted in bri1-RNAi lines as well. Increased and localized accumulation of BES1: YFP, a BR responsive marker, in the developing ligule/auricle region suggests that BR signaling is central to auricle development. For BIN2, a GSK3-like kinase, phylogenetic analyses suggested that there are 10 homologs in maize. NJ method divided BIN2 homologs into four clades with 5 members belonging to Clade II , whose members perform primary BR signaling functions in Arabidopsis. All these members had SIWID domain, which is unique to Clade II. bin2-RNAi plants had shorter stature, which was unexpected because BIN2 is a negative regulator of BR signaling. However tassel internodes and leaves were longer as expected for increased BR signaling. In contrast to bri1-RNAi plants, bin2-RNAi plants had larger auricles. bin2-RNAi plants also had changed kernel traits, too. When bin2-RNAi lines used as female, kernels on the cob independent of their genotype were larger, opaque, and had pointy ends. SEM analysis revealed that these opaque kernels were lacking a normal horny endosperm and their starch granules were larger, less compact, and non-spherical compared to non-opaque kernels granules. The bin2-RNAi transgene rescued the mild bri1-RNAi phenotype consistent with the predicted position of BIN2 downstream of BRI1 in the signaling pathway. A kinematic analysis on leaf #4 of both bri1-RNAi and bin2-RNAi showed that leaf elongation rate (LER) was increased 14% in bin2-RNAi lines, whereas decreased 17% in bri1-RNAi lines. Both cell division and cell elongation contributed to the effects on leaf length in each line. These results suggest that BR signaling has similar as well as unique roles in maize development compared to other species

Brassinosteroid regulation of plant height in maize

Brassinosteroids (BRs) are a type of phytohormone that has important roles in plant development. Even though they are well studied in model species, their role in maize development is poorly understood. To address this issue, two approaches were undertaken. Since it was shown mutations in BRs biosynthesis or signaling cause dwarfism in other plants, novel maize dwarf mutants were screened to see if they are related to the BRs. Phenotypic and genetic characterization led to the identification and genetic mapping of at least 2 likely candidates. The results of this work are presented in Chapter 2. In the second part, a transgenic approach was pursued. Four genes related to the either BR biosynthesis or signaling were manipulated by overexpression or RNAi suppression to investigate their roles in the growth and development of maize. The preliminary results suggest that similar to other plants, BRs also regulate plant height in maize. In addition, they appear to influence reproductive development and leaf morphology. This work is shown in Chapter 3. This and future studies based on the results shown here will help provide an understanding of BR\u27s role in maize development

RNA interference knockdown of BRASSINOSTEROID INSENSITIVE1 in maize reveals novel functions for brassinosteroid signaling in controlling plant architecture

Brassinosteroids (BRs) are plant hormones involved in various growth and developmental processes. The BR signaling system is well established in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) but poorly understood in maize (Zea mays). BRASSINOSTEROID INSENSITIVE1 (BRI1) is a BR receptor, and database searches and additional genomic sequencing identified five maize homologs including duplicate copies of BRI1 itself. RNA interference (RNAi) using the extracellular coding region of a maize zmbril complementary DNA knocked down the expression of all five homologs. Decreased response to exogenously applied brassinolide and altered BR marker gene expression demonstrate that zmbriI-RNAi transgenic lines have compromised BR signaling. zmbriI-RNAi plants showed dwarf stature due to shortened internodes, with upper internodes most strongly affected. Leaves of zmbriI-RNAi plants are dark green, upright, and twisted, with decreased auricle formation. Kinematic analysis showed that decreased cell division and cell elongation both contributed to the shortened leaves. A BRASSINOSTEROID INSENSITIVE1-ETHYL METHANESULFONATE-SUPPRESSOR1-yellow fluorescent protein (BES1-YFP) transgenic line was developed that showed BR-inducible BES1-YFP accumulation in the nucleus, which was decreased in zmbriI-RNAi. Expression of the BES1-YFP reporter was strong in the auricle region of developing leaves, suggesting that localized BR signaling is involved in promoting auricle development, consistent with the zmbriI-RNAi phenotype. The blade-sheath boundary disruption, shorter ligule, and disrupted auricle morphology of RNAi lines resemble KNOTTED1-LIKE HOMEOBOX (KNOX) mutants, consistent with a mechanistic connection between KNOX genes and BR signaling

Regulation of shoot development in maize via brassinosteroid signaling

Brassinosteroids (BR) are a class of phytohormones with many important roles in plant growth and development. Compared to other model organisms BR signaling is poorly understood in maize. To study BR signaling's role in maize growth and development we suppressed two members of the BR signaling pathway, BRI1 and BIN2, by RNAi approach. BLAST searches and phylogenetic analyses suggested that there are two BRI1 copies and three BRI1-like genes (BRL) homologs in maize. bri1b, which is located on chr 5, was incomplete in databases, but via subsequent cloning and sequencing was found to be an intact and expressed gene. These two closely related bri1 homologs, named bri1a and bri1b, share 93% amino acid identity and 95% similarity. Suppression of BRI1 homologs lead to dwarf plants with upright, dark green, and thicker leaves. Blade/sheath boundary was disrupted in bri1-RNAi lines as well. Increased and localized accumulation of BES1: YFP, a BR responsive marker, in the developing ligule/auricle region suggests that BR signaling is central to auricle development. For BIN2, a GSK3-like kinase, phylogenetic analyses suggested that there are 10 homologs in maize. NJ method divided BIN2 homologs into four clades with 5 members belonging to "Clade II", whose members perform primary BR signaling functions in Arabidopsis. All these members had SIWID domain, which is unique to Clade II. bin2-RNAi plants had shorter stature, which was unexpected because BIN2 is a negative regulator of BR signaling. However tassel internodes and leaves were longer as expected for increased BR signaling. In contrast to bri1-RNAi plants, bin2-RNAi plants had larger auricles. bin2-RNAi plants also had changed kernel traits, too. When bin2-RNAi lines used as female, kernels on the cob independent of their genotype were larger, opaque, and had pointy ends. SEM analysis revealed that these opaque kernels were lacking a normal horny endosperm and their starch granules were larger, less compact, and non-spherical compared to non-opaque kernels granules. The bin2-RNAi transgene rescued the mild bri1-RNAi phenotype consistent with the predicted position of BIN2 downstream of BRI1 in the signaling pathway. A kinematic analysis on leaf #4 of both bri1-RNAi and bin2-RNAi showed that leaf elongation rate (LER) was increased 14% in bin2-RNAi lines, whereas decreased 17% in bri1-RNAi lines. Both cell division and cell elongation contributed to the effects on leaf length in each line. These results suggest that BR signaling has similar as well as unique roles in maize development compared to other species.</p

Brassinosteroid regulation of plant height in maize

Brassinosteroids (BRs) are a type of phytohormone that has important roles in plant development. Even though they are well studied in model species, their role in maize development is poorly understood. To address this issue, two approaches were undertaken. Since it was shown mutations in BRs biosynthesis or signaling cause dwarfism in other plants, novel maize dwarf mutants were screened to see if they are related to the BRs. Phenotypic and genetic characterization led to the identification and genetic mapping of at least 2 likely candidates. The results of this work are presented in Chapter 2. In the second part, a transgenic approach was pursued. Four genes related to the either BR biosynthesis or signaling were manipulated by overexpression or RNAi suppression to investigate their roles in the growth and development of maize. The preliminary results suggest that similar to other plants, BRs also regulate plant height in maize. In addition, they appear to influence reproductive development and leaf morphology. This work is shown in Chapter 3. This and future studies based on the results shown here will help provide an understanding of BR's role in maize development.</p

Intrapericardial teratoma in a newborn: a case report

Oto O, Guzeloglu M, Kir M, Metin K, Cakmakci H, Albayrak G, Koc A. Intrapericardial teratoma in a newborn: a case report. Mirk J Pediatr 2012; 54: 71-73

RNA Interference Knockdown of BRASSINOSTEROID INSENSITIVE1 in Maize Reveals Novel Functions for Brassinosteroid Signaling in Controlling Plant Architecture

WOS: 000360930600062PubMed ID: 26162429Brassinosteroids (BRs) are plant hormones involved in various growth and developmental processes. The BR signaling system is well established in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) but poorly understood in maize (Zea mays). BRASSINOSTEROID INSENSITIVE1 (BRI1) is a BR receptor, and database searches and additional genomic sequencing identified five maize homologs including duplicate copies of BRI1 itself. RNA interference (RNAi) using the extracellular coding region of a maize zmbril complementary DNA knocked down the expression of all five homologs. Decreased response to exogenously applied brassinolide and altered BR marker gene expression demonstrate that zmbriI-RNAi transgenic lines have compromised BR signaling. zmbriI-RNAi plants showed dwarf stature due to shortened internodes, with upper internodes most strongly affected. Leaves of zmbriI-RNAi plants are dark green, upright, and twisted, with decreased auricle formation. Kinematic analysis showed that decreased cell division and cell elongation both contributed to the shortened leaves. A BRASSINOSTEROID INSENSITIVE1-ETHYL METHANESULFONATE-SUPPRESSOR1-yellow fluorescent protein (BES1-YFP) transgenic line was developed that showed BR-inducible BES1-YFP accumulation in the nucleus, which was decreased in zmbriI-RNAi. Expression of the BES1-YFP reporter was strong in the auricle region of developing leaves, suggesting that localized BR signaling is involved in promoting auricle development, consistent with the zmbriI-RNAi phenotype. The blade-sheath boundary disruption, shorter ligule, and disrupted auricle morphology of RNAi lines resemble KNOTTED1-LIKE HOMEOBOX (KNOX) mutants, consistent with a mechanistic connection between KNOX genes and BR signaling.Iowa State University Plant Sciences Institute; Genetics, Development, and Cell Biology Department; Ministry of National Education, Republic of TurkeyMinistry of National Education - TurkeyThis work was supported by the Iowa State University Plant Sciences Institute and the Genetics, Development, and Cell Biology Department and by the Ministry of National Education, Republic of Turkey (education fellowship to G.K.)