The genetic regulation of Kranz anatomy in maize
<p>The C<sub>4</sub> photosynthetic pathway acts to concentrate CO<sub>2</sub> around the enzyme Ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), ensuring that it catalyses a carboxylation rather than oxygenation reaction, which in turn suppresses photorespira...
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| Format: | Thesis |
| Language: | English |
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2016
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| _version_ | 1797079746162458624 |
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| author | Hughes, T |
| author2 | Langdale, J |
| author_facet | Langdale, J Hughes, T |
| author_sort | Hughes, T |
| collection | OXFORD |
| description | <p>The C<sub>4</sub> photosynthetic pathway acts to concentrate CO<sub>2</sub> around the enzyme Ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), ensuring that it catalyses a carboxylation rather than oxygenation reaction, which in turn suppresses photorespiration. In nearly all cases C<sub>4</sub> photosynthesis is underpinned by characteristic Kranz anatomy, with concentric wreaths of bundle sheath (BS) and mesophyll (M) cells surrounding closely spaced veins. The increased yields associated with the C<sub>4</sub> pathway have lead to the suggestion that C<sub>3</sub> crops such as rice should be engineered to undertake C<sub>4</sub> photosynthesis, however, this goal is currently held back by a lack of understanding about how the development of Kranz anatomy is regulated. </p> <p>Recently, a number of candidate Kranz regulators have been identified in an RNA-seq study that compared leaf development in maize foliar (Kranz) and husk (non-Kranz) leaves. However, this study did not consider the impact of a recent whole genome duplication in the maize lineage on the gene expression patterns analysed. Therefore, in this thesis maize homeolog gene-pair divergence during early leaf development was assessed. This revealed that expression divergence of homeolog gene-pairs is a significant evolutionary phenomenon. </p> <p>Functional validation of a subset of Kranz candidates revealed that a <em>Zmscr1-1</em>; <em>Zmscr1h-1</em> double mutant exhibited defects in Kranz patterning, including increased formation of extra BS cells and veins with no separating M cells. Furthermore, <em>Zmnkd1</em>; <em>Zmnkd2</em> double mutants exhibited a subtle increase in extra BS cell formation. Taken together, this indicates that both <em>ZmSCR1/ZmSCR1h</em> and <em>ZmNKD1/ZmNKD2</em> function redundantly during Kranz development. No evidence was obtained that two additional genes, <em>ZmSHR2</em> and <em>ZmRVN1</em>, play a role in Kranz development, and expression of candidate Kranz regulators in rice did not alter leaf anatomy. Together, this work has confirmed roles for a number of genes in Kranz regulation, and has provided insight into the complex regulation underpinning Kranz development in maize.</p> |
| first_indexed | 2024-03-07T00:50:09Z |
| format | Thesis |
| id | oxford-uuid:86184e64-c7bb-43e9-9320-0ebbb2793ea8 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T00:50:09Z |
| publishDate | 2016 |
| record_format | dspace |
| spelling | oxford-uuid:86184e64-c7bb-43e9-9320-0ebbb2793ea82022-03-26T22:01:55ZThe genetic regulation of Kranz anatomy in maizeThesishttp://purl.org/coar/resource_type/c_db06uuid:86184e64-c7bb-43e9-9320-0ebbb2793ea8C4 photosynthesisLeaf developmentEnglishORA Deposit2016Hughes, TLangdale, J<p>The C<sub>4</sub> photosynthetic pathway acts to concentrate CO<sub>2</sub> around the enzyme Ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco), ensuring that it catalyses a carboxylation rather than oxygenation reaction, which in turn suppresses photorespiration. In nearly all cases C<sub>4</sub> photosynthesis is underpinned by characteristic Kranz anatomy, with concentric wreaths of bundle sheath (BS) and mesophyll (M) cells surrounding closely spaced veins. The increased yields associated with the C<sub>4</sub> pathway have lead to the suggestion that C<sub>3</sub> crops such as rice should be engineered to undertake C<sub>4</sub> photosynthesis, however, this goal is currently held back by a lack of understanding about how the development of Kranz anatomy is regulated. </p> <p>Recently, a number of candidate Kranz regulators have been identified in an RNA-seq study that compared leaf development in maize foliar (Kranz) and husk (non-Kranz) leaves. However, this study did not consider the impact of a recent whole genome duplication in the maize lineage on the gene expression patterns analysed. Therefore, in this thesis maize homeolog gene-pair divergence during early leaf development was assessed. This revealed that expression divergence of homeolog gene-pairs is a significant evolutionary phenomenon. </p> <p>Functional validation of a subset of Kranz candidates revealed that a <em>Zmscr1-1</em>; <em>Zmscr1h-1</em> double mutant exhibited defects in Kranz patterning, including increased formation of extra BS cells and veins with no separating M cells. Furthermore, <em>Zmnkd1</em>; <em>Zmnkd2</em> double mutants exhibited a subtle increase in extra BS cell formation. Taken together, this indicates that both <em>ZmSCR1/ZmSCR1h</em> and <em>ZmNKD1/ZmNKD2</em> function redundantly during Kranz development. No evidence was obtained that two additional genes, <em>ZmSHR2</em> and <em>ZmRVN1</em>, play a role in Kranz development, and expression of candidate Kranz regulators in rice did not alter leaf anatomy. Together, this work has confirmed roles for a number of genes in Kranz regulation, and has provided insight into the complex regulation underpinning Kranz development in maize.</p> |
| spellingShingle | C4 photosynthesis Leaf development Hughes, T The genetic regulation of Kranz anatomy in maize |
| title | The genetic regulation of Kranz anatomy in maize |
| title_full | The genetic regulation of Kranz anatomy in maize |
| title_fullStr | The genetic regulation of Kranz anatomy in maize |
| title_full_unstemmed | The genetic regulation of Kranz anatomy in maize |
| title_short | The genetic regulation of Kranz anatomy in maize |
| title_sort | genetic regulation of kranz anatomy in maize |
| topic | C4 photosynthesis Leaf development |
| work_keys_str_mv | AT hughest thegeneticregulationofkranzanatomyinmaize AT hughest geneticregulationofkranzanatomyinmaize |