Improving plant propagation through the manipulation of the genetic and physical environment

Open Access
Author:
Florez, Sergio L
Graduate Program:
Chemical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 04, 2015
Committee Members:
  • Wayne Roger Curtis, Dissertation Advisor
  • Wayne Roger Curtis, Committee Chair
  • Mark Guiltinan, Committee Member
  • Andrew Zydney, Committee Member
  • Esther Winter Gomez, Committee Member
  • Siela Maximova, Committee Member
Keywords:
  • Somatic Embryogenesis
  • Temporary Immersion Bioreactor
  • Cacao
  • Transient Expression
Abstract:
Sustaining the increasing global population poses a daunting challenge. As food demands increase, we need to produce better plants while consuming fewer resources. The “producing more with less” dilemma makes this problem very hard to address. Fortunately, over the last several decades, scientists have been developing elite varieties of plants that are higher yielding, drought tolerant, and resistant to pathogens. The discovery and generation of these elite varieties are only a part of the solution. Producing these superior plants at the scale needed to meet the growing demand also presents another challenge. The processes of plant propagation has some inherent problems: The process is long and laborious; the end product is of low monetary value; and traditional methods could give rise to genetic heterogeneity, which results in loss of desired plant characteristics. To deal with these obstacles, new micropropagation techniques have been developed to make plant propagation more efficient. However, these techniques are not universal for all plant species and require a considerable amount of time to develop. In some cases, the method has to be optimized for different genotypes of the same specie. These techniques can also result in a decrease in plant quality, particularly, poor development which leads to low conversion rates. This dissertation will suggest a novel genetic approach to improve plant propagation by understanding the important factors that control plant production and development. To test this strategy, Theobroma cacao (the tree that gives us chocolate) was used as a plant model. Finally, from an engineering point of view, a novel bioreactor design was developed as a way to make the process more efficient by increasing yield/quality and lowering costs by automation and scale-up. The work of this dissertation is summarized: • A whole genome microarray was used to study zygotic and somatic embryogenesis (SE) to understand the poor conversion rates in cacao somatic embryogenesis. • A set of biomarkers was identified to help study the process of somatic embryogenesis in cacao. • A novel strategy based on transient expression of a transcription factor was developed and demonstrated to improve embryo productivity in cacao. • An inducible system that initiates SE based on gene overexpression was developed to help study the process of SE as well as help further research with cacao. • A novel low-cost temporary immersion bioreactor (TIB) was designed to overcome mass transfer limitations and shear sensitivity while, reducing costs by using gravity driven liquid flow. This allowed the decoupling of gas and liquid flow and translates to significant savings in gas consumption and better manipulation of the physical environment. • The versatility of the TIB was demonstrated by improving heterotrophic and photoautotrophic growth in Nictoiana benthamiana and watermelon, respectively.