Progress 07/15/03 to 07/14/05
Outputs
The normal development of leaves and other lateral organs of the shoot requires the simultaneous repression of meristem-specific genes and the activation of organ-specific genes. Lateral organ initiation and patterning must therefore involve communication between the shoot apical meristem (SAM) and initiating organ primordia. The goal of this project was to characterize the function of two Arabidopsis genes, AtMYB105 and AtMYB117, which are now called LATERAL ORGAN FUSION1 (LOF1) and LATERAL ORGAN FUSION2 (LOF2). LOF1 and LOF2 are expressed in a domain between the SAM and lateral organs. These genes encode MYB-domain proteins that are predicted to function in transcriptional regulation. We showed that mutations in LOF1 result in fusions of lateral inflorescence branches to the subtending cauline leaf and in vascular patterning defects. In contrast, mutation of LOF2 does not result in a visible phenotype. Plants that are homozygous for mutations in both LOF1 and LOF2
have a novel phenotype, fusion of the flower pedicel to the inflorescence stem, suggesting that these two genes have overlapping functions. We have focused on understanding the relationship between LOF1, LOF2, and other genes that control meristem function and organ separation in Arabidopsis. Mis-expression of LOF1 and LOF2 resulted in organ patterning defects as well. We found that the LOF1 protein interacts with LOB, another protein that is expressed in organ boundaries. My lab has recently shown that LOB is a transcription factor, and we are currently searching for genes that are regulated by LOB and LOF1. We showed that LOF1 expression is regulated by the KNOX transcription factors BREVIPEDICELLUS (BP) and SHOOT MERISTEMLESS (STM), implicating LOF1 in the regulation of meristem maintenance and organ initiation. In addition LOF1 expression is regulated by PENNYWISE (PNY) and POUNDFOOLISH (PNF), two homeodomain transcription factors that function together with BP and STM to maintain
meristem identity and internode patterning. Double mutants have been informative in understanding these relationships. The lof1 mutation suppresses the pny and pnf mutant phenotypes, indicating that LOF1 misexpression is responsible for the defects found in pny and pnf mutants. We also found that mutations in the LATERAL SUPPRESSOR (LAS) gene dramatically enhances the phenotype of lof1. LAS encodes a transcription factor expressed at organ boundaries and we are currently investigating the molecular relationship between LOF1 and LAS.
Impacts
Understanding the role of LATERAL ORGAN FUSION1 and LATERAL ORGAN FUSION2, transcription factors that are expressed in a domain between the shoot apical meristem and lateral organs, will lead to an enhanced understanding of the important process of leaf initiation and patterning.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
The normal development of leaves and other lateral organs of the shoot requires the simultaneous repression of meristem-specific genes and the activation of organ-specific genes. Lateral organ initiation and patterning must therefore involve communication between the shoot apical meristem (SAM) and initiating organ primordia. The goal of this project is to characterize the function of two Arabidopsis genes, AtMYB105 and AtMYB117, which are expressed in a domain between the SAM and lateral organs. These genes encode MYB-domain proteins that are predicted to function in transcriptional regulation. We have previously shown that mutation of MYB105 does not cause a visible phenotype, while mutations in MYB117 result in fusions of lateral inflorescence branches to the subtending cauline leaf. Plants that are homozygous for mutations in both MYB105 and MYB117 have a novel phenotype, fusion of the flower pedicel to the inflorescence stem, suggesting that these two genes have
overlapping functions. MYB117 and MYB105 have been named LATERAL ORGAN FUSION1 (LOF1) and LOF2, respectively, to reflect these phenotypes. In the past year, we have focused on obtaining a detailed characterization of the expression patterns of LOF1 and LOF2, and in understanding the relationship between LOF1, LOF2, and genes that control meristem function and organ separation. We have found that LOF1 expression is regulated by the KNOX transcription factors BREVIPEDICELLUS and SHOOT MERISTEMLESS, implicating LOF1 in the regulation of meristem maintenance and organ initiation. Double mutants have been constructed between lof1 or lof2 mutants and a suite of meristem and organ polarity mutants. Analysis of the resulting double mutants for the presence of new phenotypes is currently underway.
Impacts
Understanding the role of LATERAL ORGAN FUSION1 and LATERAL ORGAN FUSION2, transcription factors that are expressed in a domain between the shoot apical meristem and lateral organs, will lead to an enhanced understanding of the important process of leaf initiation and patterning. This understanding could eventually enable the engineering of modified or novel traits in crop plants.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The normal development of leaves and other lateral organs of the shoot requires the simultaneous repression of meristem-specific genes and the activation of organ-specific genes. Lateral organ initiation and patterning must therefore involve communication between the shoot apical meristem (SAM) and initiating organ primordia. The goal of this project is to characterize the function of two Arabidopsis genes, AtMYB105 and AtMYB117, which are expressed in a domain between the SAM and lateral organs. These genes encode MYB-domain proteins that are predicted to function in transcriptional regulation. We have characterized several T-DNA insertions in MYB105 and MYB117. One insertion in MYB105 (myb105-1) is likely to result in a null mutation, as MYB105 transcripts are not detectable in homozygous plants. The other mutations have less dramatic effects on transcript levels, and all subsequent work will be done using the myb105-1 allele. No clear phenotypes have yet been
observed in myb105-1 homozygous plants. Of the three insertions in MYB117, only one affects transcript levels appreciably, causing an approximate 70% reduction. This allele, myb117-1, while clearly not a null, displays intriguing phenotypes. myb117-1 homozygous plants show fusion of the lateral inflorescence branches to the subtending cauline leaf, as well as a suppression of accessory bud formation. This phenotype indicates that MYB117 plays a role in separation of lateral organs, consistent with its expression in organ boundaries. Intriguingly, a myb105-1 myb117-1 double mutant displays a unique phenotype not present in either single mutant: fusion of the flower pedicel to the stem. These results indicate that MYB105 and MYB117 are partially redundant. To characterize interactions between MYB105, MYB117, and genes that control meristem function and organ separation, double mutants have constructed between the myb mutants and brevipedicellus, shoot meristemless, bellringer/pennywise,
lateral suppressor, and polarity mutants. Expression analysis of these genes in MYB mutants and over-expression plants is also ongoing.
Impacts
Understanding the role of AtMYB105 and AtMYB117, transcription factors that are expressed in a domain between the shoot apical meristem and lateral organs, will lead to an enhanced understanding of the important process of leaf initiation and patterning. This understanding could eventually enable the engineering of modified or novel traits in crop plants.
Publications
- No publications reported this period
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