Document Type

Dissertation - Open Access

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School

Biology and Microbiology

First Advisor

Yajun Wu


Alfalfa, flowering, hydrotropism, low temperature, Maize


Plants constantly engage and interact with the environment and respond to the changes in conditions like temperature, water, and photoperiod, by regulating expression of genes of multiple regulatory and signaling pathways. Insight into these pathways and their participants has provided and will provide candidates to improve various agronomically important traits in crops through marker-assisted breeding and genetic manipulation. With this aim in mind, in the present study, I attempted to identify key candidate genes that are involved in the regulation of; i) plant response to low temperature stress, ii) plant roots’ response to soil moisture content and iii) flowering time. identified and studied the expression of C-repeat binding factors (CBFs)-like genes and CONSTANS (CO)-, FVE- and FCA-like genes in alfalfa (Medicago sativa L.), a major forage crop in United States and worldwide. C-repeat binding factors (CBFs) are key transcription factors involved in plants’ response to low temperatures. The results based on the gene expression and its correlation with freezing tolerance in alfalfa suggested that two MsCBFl genes might play important role in freezing tolerance in alfalfa. Through expression analysis of CO-like, FVE-like and FCA-like genes in different tissues, at differential stages, and under circadian control, I identified several genes in CO-, FVE- and FCA-like gene families that are potential functional homologues involved in flowering time control. These candidate genes, once function is confirmed, can be used to delay flowering in alfalfa which will lead to higher biomass production and higher quality forage due to delayed senescence, a trait associated with flowering. An enhancement in biomass production can also pave the way for its use in cellulosic-based biofuel production. To understand the molecular basis of plant roots’ response to soil moisture gradient in major crops, a phenomenon known as hydrotropism, I attempted to identify the functional homologue of Arabidopsis MIZ1, one of the key regulators of hydrotropism, in maize (Zea mays L.). Through analysis of expression of MIZ1-like genes in maize, one gene, ZmMIZ1l-K appeared to be the candidate functioning in hydrotropic response. This study is the first attempt at understanding molecular players in hydrotropism in a crop plant and could be potentially used to enhance water acquisition of crop plants and thus their performance especially under drought conditions. My research demonstrated that the candidate gene approach I took can be a first step to effectively identify the key players in the regulatory pathways in major crops. Through studying these genes, I also provided great insight into the complexity of molecular processes in responding to environmental cues in crop plants. Additional studies are needed to confirm the gene functionalities and their key roles in these processes. The molecular participants can then be used as resources to develop better crop varieties that could perform efficiently especially under more severe environmental stresses like drought and harsh temperatures.

Library of Congress Subject Headings

Plants -- Effect of stress on -- Molecular aspects.
Gene expression.
Alfalfa -- Effect of cold on.
Alfalfa -- Flowering time.
Corn -- Effect of soil moisture on.


Includes bibliographical references



Number of Pages



South Dakota State University



Rights Statement

In Copyright