Understanding the genetic factors involved in cell wall biosynthesis and biomass production

Plants are sessile hence need to adapt to the rapid environmental changes. Cell walls are the primary barriers that protect plants from biotic and abiotic stressors and withstand internal turgor pressure which drives plant cell growth by cell expansion. Recently, plants cell walls have been utilized as natural source for renewable energy production. Plant cell walls are made of both sugar-based polymers such as cellulose, hemicellulose, pectin and phenolic biopolymer lignin. These cell wall polymers are regulated by various biosynthetic genes which are further regulated by master transcription factors which can sense environmental changes and modulate plant growth through concomitant deposition of cell wall that ultimately determines the plant biomass yield. Since cell wall polymers are derived from photosynthetic glucose, plant photoreceptor based light perception and signal transduction play a major role in regulating plant growth that is associated with cell wall polymer biosynthesis. The dissertation focused on understanding the genetic factors involved in cell wall biosynthesis and biomass production in plants. Using forward genetics approach, we found FKF1, a blue light photoreceptor, that when mutated regulates cell wall biosynthesis with particular emphasis on cellulose biosynthesis. FKF1 is a well-known flowering time regulator. In another objective, PHYB, a red-light photoreceptor, that when mutated does not perceive red light and shown to negatively regulates overall cell division process, thereby reducing the overall plant biomass yield. These two objectives discovered light on the role of photoreceptors that regulates cellulose biosynthesis and overall cell division process which are two major factors that determine plant biomass yield. However, the exact mechanism through which these two major photoreceptors regulate these processes needs to be further investigated. The third objective of this dissertation investigated the gene expression analysis of developing cotton fiber, an interesting model cell for cell wall biosynthesis. The investigation led to the discovery of interesting laccases as candidates for further investigation. Selected candidate laccase (Ga_LAC17_05) from cotton and its functional role and relationship with phenolic acids were explored using dicot model Arabidopsis thaliana. In summary, the plant cell walls are important source of renewable bioenergy and the discovery of regulation by environmental responsive genes such as photoreceptors which work through various mechanisms to regulate their biosynthesis process in an important step to understand the environmental regulation of cell wall biosynthesis and biomass production.

This dissertation won 2nd Place in the Texas Tech University Outstanding Thesis and Dissertation Award, Biological Life Sciences, 2019.

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