Dissertation
Vegetative phase change timing in maize integrates several leaf-derived signals and molecular processes
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2021
DOI: 10.17077/etd.006241
Abstract
After germination, plants proceed through a series of developmental stages before flowering. In angiosperms, the first transition occurs during the vegetative phase where the shoot matures from the juvenile to the adult phase, called vegetative phase change (VPC). In maize, both phases consist of easily scored morphological characteristics that led to the discovery of underlying genetic networks, including two phase-specific microRNAs. The expression of miR156 is high during the juvenile phase and the decline in miR156 and subsequent increase in miR172 expression marks the transition into the adult phase, where miR172 represses transcripts that direct juvenile traits. Why miR156 levels become high and what facilitates the decrease in expression remains an open question, but work in other species suggest hormones, stress, and sugar direct epigenetic modifiers to set the timing of VPC. In maize, transcripts of genes that remediate oxidative stress and facilitate jasmonic acid (JA) signaling are more abundant in juvenile compared to adult leaf primordia. To test the hypothesis that JA promotes juvenility, I characterized this hormone and markers of oxidative stress. Additionally, I analyzed expression patterns of leaf primordia from each phase to elucidate developmental patterns that propagate phase specific gene expression that may influence phase identity. Finally, I investigated the role of hydrogen sulfide in early seedling growth and VPC. I concluded that the hormone JA is a leaf derived signal that influences the duration of the juvenile phase of maize, characterized patterns of genes expression data specific to each phase, and found that while hydrogen sulfide reduces the time to germination and results in fast early seedling growth in multiple plants, it does not have a role in vegetative phase change.
Details
- Title: Subtitle
- Vegetative phase change timing in maize integrates several leaf-derived signals and molecular processes
- Creators
- Krista Osadchuk
- Contributors
- Erin E Irish (Advisor)Lori Adams (Committee Member)Chi-Lien Cheng (Committee Member)Douglas Houston (Committee Member)Timothy Mattes (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Biology
- Date degree season
- Autumn 2021
- DOI
- 10.17077/etd.006241
- Publisher
- University of Iowa
- Number of pages
- xii, 178 pages
- Copyright
- Copyright 2021 Krista Osadchuk
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 133-159)
- Public Abstract (ETD)
Most life on this planet is marked by a series of developmental stages, and vegetative life is no exception. Most land plants undergo a period of juvenility during which cues to reproduce cannot be integrated into a physiological response, similar to humans. After proceeding through vegetative phase change (VPC), a comparable transition to puberty, plants are able to integrate internal cues and/or cues from the environment to develop flowers and fruits - the site of reproduction. While development in the juvenile phase is imperative for a robust and healthy life, the years-long juvenile phase in some trees poses an obstacle in breeding programs aimed at creating genetic variations of trees that are able to withstand pests and changes in climate. Since genomes of some plants are large and harder to successfully manipulate with contemporary genome editing technology (ie. CRISPR), classic breeding programs must still be utilized to help species survive in our current environment. Maize, an important cereal crop, shares many pathways in common with woody perennials and has a fast generation time. Thus, important findings can be translated to these larger organisms. Here, I investigated leaf-derived signaling using a combination of biochemistry and bioinformatics to uncover patterns that direct or influence the phase of the shoot. High levels and dynamic signaling patterns of the hormones jasmonic acid and gibberellic acid suggest they promote the juvenile phase and vegetative phase change, respectively. Oxidative stress caused by elevated levels of reactive oxygen species is characteristic of the juvenile phase and may influence vegetative phase change timing. Surprisingly, hydrogen sulfide appears to play a significant role in germination and early seedling establishment possibly by relieving oxidative stress and acting as an electron donor in cyclic electron flow during photosynthesis in expanding early juvenile leaves.
- Academic Unit
- Biology
- Record Identifier
- 9984210641002771
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