Abstract
ABSTRACT OF THE DISSERTATIONCharacterization of LATERAL ORGAN BOUNDARIES (LOB) and leaflet inclination in Vigna unguiculata (L.) Walp (Cowpea)ByMichael Frederick SchwartzPlants undergo organogenesis throughout their lifetime by maintaining populations of pluripotent cells at their apices. The shoot apical meristem (SAM) produces lateral organs, such as leaves, which form at the periphery of the SAM. The SAM and the lateral organs are separated by the boundary region. The boundary region contains a population of cells which are smaller and divide infrequently and is a region of reduced growth. The boundary region plays an important role in regulating shoot architecture as it is the region of the plant that influences leaf inclination. The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB) is expressed in plant organ boundaries and functions to limit growth and separate the organs. This dissertation focuses on characterizing an ortholog of LOB, VuLOB, in cowpea, an economically important legume, and its role in regulating leaf inclination. In chapter 1, I identify the LOB ortholog in cowpea, termed VuLOB, through the identification of the LOB-domain genes in cowpea and phylogenetic analysis. Characterization of the expression pattern of VuLOB shows transcript accumulation in the pulvini, structures at the base of the leaves and leaflets which incline the leaves under water-deficit. VuLOB is positively regulated by the phytohormone brassinosteroid (BR) which mimics LOB’s regulation, but functional analysis using Arabidopsis suggests that VuLOB may not form the boundary by restricting growth. VuLOB transcripts are not significantly changed in inclined pulvini. BRs have been shown to regulate leaf inclination in the grasses. When BRs are removed from cowpea using propiconazole they fail to incline. Propiconazole treatment changes the cellular morphology of the epidermis of the pulvinus which correlates with the failure to incline. This suggests that BRs are required to promote leaf inclination in cowpea In chapter 2, I use genome-wide association studies (GWAS) to identify regions of the cowpea genome which correlate with the variation in the size of the pulvinus and leaflet inclination after water-deficit. Several significant peaks were identified which correlate to the variation in pulvinus size, but no peaks were identified with regards to leaflet angle. From the significant peaks a candidate gene, VuLBD41, was identified. VuLBD41 is a LOB-domain transcription factor that is orthologous to the Arabidopsis transcription factors LBD40 and LBD41. Transcripts of VuLBD41 accumulate in the pulvini of cowpea. However, functional analysis using Arabidopsis did not reveal any function in regard to development. Transgenic plants overexpressing VuLBD41 appear morphologically normal. This suggests that VuLBD41 has an unknown role in boundary formation. In chapter 3, I characterize the genetic relationship between LOB and 2 putative targets, TREHALOSE-6-PHOSPHATE PHOSPHATASE I/J (TPPI and TPPJ). LOB directly regulates TPPJ, but not TPPI in yeast. However, higher order mutants don’t have an enhancement of the organ fusions found in lob mutant plants, but they do have a significant increase in the number of branches, which suggests that they have some role in the boundary. Further, I show that ectopic TPPJ accumulation in the boundary is sufficient to rescue the lob mutant phenotype. This suggests that LOB requires TPPJ to restrict growth at the boundary.
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Claims 20
Claim · model-written summary
VuLOB shows transcript accumulation in cowpea pulvini.
- Taxon
- Vigna unguiculata
Vigna unguiculatat1 - Organ / stage
- pulvinie2
- Gene
- VuLOBe2
- Outcome
- transcript accumulatione2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“Characterization of the expression pattern of VuLOB shows transcript accumulation in the pulvini”
Claim · model-written summary
VuLOB is positively regulated by brassinosteroid in cowpea.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Gene
- VuLOBe2
- Compound
- brassinosteroide2
- Outcome
- regulatede2
- Direction
- positivelye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“VuLOB is positively regulated by the phytohormone brassinosteroid (BR)”
Claim · model-written summary
VuLOB may not form the boundary by restricting growth, based on Arabidopsis functional analysis.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Gene
- VuLOBe2
- Outcome
- form the boundary by restricting growthe2
- Qualifier
- functional analysis using Arabidopsise2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“functional analysis using Arabidopsis suggests that VuLOB may not form the boundary by restricting growth”
Claim · model-written summary
VuLOB transcripts are not significantly changed in inclined cowpea pulvini.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Organ / stage
- inclined pulvinie2
- Outcome
- VuLOB transcriptse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“VuLOB transcripts are not significantly changed in inclined pulvini”
Claim · model-written summary
Removing brassinosteroids from cowpea with propiconazole prevented leaf inclination.
- Taxon
- cowpeaVigna unguiculatae2
- Treatment
- propiconazolee2
- Compound
- BRse2
- Outcome
- inclinee2
- Direction
- decreaseinferrede2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“When BRs are removed from cowpea using propiconazole they fail to incline”
Claim · model-written summary
Propiconazole treatment changes epidermal cell morphology of the pulvinus, correlating with failure to incline in cowpea.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Organ / stage
- epidermis of the pulvinuse2
- Treatment
- Propiconazole treatmente2
- Outcome
- cellular morphology of the epidermise2
- Direction
- changese2
- Qualifier
- correlates with the failure to inclinee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“Propiconazole treatment changes the cellular morphology of the epidermis of the pulvinus which correlates with the failure to incline”
Claim · model-written summary
GWAS identified significant peaks correlating with variation in cowpea pulvinus size.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Organ / stage
- pulvinuse2
- Outcome
- variation in pulvinus sizee2
- Direction
- correlatee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“Several significant peaks were identified which correlate to the variation in pulvinus size”
Claim · model-written summary
No GWAS peaks were identified for cowpea leaflet angle after water-deficit.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Treatment
- water-deficite2
- Outcome
- leaflet anglee1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e1“no peaks were identified with regards to leaflet angle”
e2“regions of the cowpea genome which correlate with the variation in the size of the pulvinus and leaflet inclination after water-deficit”
Claim · model-written summary
A candidate gene, VuLBD41, was identified from the significant GWAS peaks in cowpea.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Gene
- VuLBD41e2
- Outcome
- candidate genee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“From the significant peaks a candidate gene, VuLBD41, was identified”
Claim · model-written summary
VuLBD41 transcripts accumulate in cowpea pulvini.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Organ / stage
- pulvinie2
- Gene
- VuLBD41e2
- Outcome
- Transcripts of VuLBD41 accumulatee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“Transcripts of VuLBD41 accumulate in the pulvini of cowpea”
Claim · model-written summary
VuLBD41 functional analysis in Arabidopsis revealed no function in development.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Gene
- VuLBD41e2
- Outcome
- any function in regard to developmente1
- Qualifier
- functional analysis using Arabidopsise1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e1“functional analysis using Arabidopsis did not reveal any function in regard to development”
e2“Transgenic plants overexpressing VuLBD41 appear morphologically normal”
Claim · model-written summary
Transgenic plants overexpressing VuLBD41 appeared morphologically normal.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Treatment
- Transgenic plants overexpressing VuLBD41e2
- Gene
- VuLBD41e2
- Outcome
- morphologically normale2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“Transgenic plants overexpressing VuLBD41 appear morphologically normal”
Claim · model-written summary
LOB directly regulates TPPJ in yeast.
- Taxon
- Arabidopsis
Arabidopsise1 - Gene
- TPPJe2
- Outcome
- directly regulatese2
- Qualifier
- in yeaste2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB)”
e2“LOB directly regulates TPPJ, but not TPPI in yeast”
Claim · model-written summary
LOB does not directly regulate TPPI in yeast.
- Taxon
- ArabidopsisArabidopsise1
- Gene
- TPPIe2
- Outcome
- directly regulatese2
- Qualifier
- in yeaste2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB)”
e2“LOB directly regulates TPPJ, but not TPPI in yeast”
Claim · model-written summary
Higher order mutants showed no enhancement of the organ fusions found in lob mutant plants.
- Taxon
- ArabidopsisArabidopsise1
- Material
- higher order mutantse2
- Outcome
- enhancement of the organ fusionse2
- Comparator
- lob mutant plantse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB)”
e2“higher order mutants don't have an enhancement of the organ fusions found in lob mutant plants, but they do have a significant increase in the number of branches”
Claim · model-written summary
Higher order mutants showed a significant increase in the number of branches.
- Taxon
- ArabidopsisArabidopsise1
- Material
- higher order mutantse2
- Outcome
- number of branchese2
- Direction
- increasee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB)”
e2“higher order mutants don't have an enhancement of the organ fusions found in lob mutant plants, but they do have a significant increase in the number of branches”
Claim · model-written summary
Ectopic TPPJ accumulation in the boundary was sufficient to rescue the lob mutant phenotype.
- Taxon
- ArabidopsisArabidopsise1
- Treatment
- ectopic TPPJ accumulation in the boundarye2
- Gene
- TPPJe2
- Outcome
- rescue the lob mutant phenotypee2
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB)”
e2“ectopic TPPJ accumulation in the boundary is sufficient to rescue the lob mutant phenotype”
Claim · model-written summary
LOB requires TPPJ to restrict growth at the boundary (authors' interpretation).
- Taxon
- ArabidopsisArabidopsise1
- Gene
- TPPJe2
- Outcome
- restrict growth at the boundarye2
- Qualifier
- LOB requires TPPJe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The Arabidopsis transcription factor LATERAL ORGAN BOUNDARIES (LOB)”
e2“This suggests that LOB requires TPPJ to restrict growth at the boundary”
Claim · model-written summary
VuLBD41 is orthologous to Arabidopsis LBD40 and LBD41.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Gene
- VuLBD41e2
- Outcome
- orthologous to the Arabidopsis transcription factors LBD40 and LBD41e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“VuLBD41 is a LOB-domain transcription factor that is orthologous to the Arabidopsis transcription factors LBD40 and LBD41”
Claim · model-written summary
The LOB ortholog in cowpea, VuLOB, was identified.
- Taxon
- Vigna unguiculataVigna unguiculatat1
- Gene
- VuLOBe2
- Outcome
- LOB orthologe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t1“Vigna unguiculata (L.) Walp”
e2“I identify the LOB ortholog in cowpea, termed VuLOB”