Date of Award

Spring 2017

Degree Type

Honors Project

School

College of Liberal Arts

First Advisor

Irina Makarevitch

Abstract

With booming populations soon to overwhelm the world's food production capabilities, studying what makes crop organisms, like maize, efficient is crucial to ensure that the demand for food is met. Planting earlier in the spring would lengthen the crop season and produce larger yields provided the crop is tolerant to early spring’s low temperatures. Plants can adjust to abiotic stresses through biochemical changes controlled by transcription of genes. Trained plants can be produced by pre-exposing them to a lesser stress, allowing them to recover, then exposing them to a greater, longer stress. It is hypothesized that trained plants will tolerate the second harder stress more than untrained plants. There are also many different lines of maize with varying degrees of cold tolerance regardless of training. For instance, B73 is known to be less cold tolerant than Mo17.

In this study, candidate cold tolerance genes were identified using RNAseq of maize seedlings exposed to multiple cold stresses. Quantitative trait loci analysis were conducted on 95 lines of the IBM population and their parents (B73 and Mo17). These analyses elucidated the differences in cold response between initial and repeated cold exposure as well as the difference between cold susceptible B73 and cold tolerant Mo17 maize lines.

Through support of phenotypic measurements (total height, leaf greenness, chlorophyll concentration, and a 3-point visual scale), it was concluded that previous cold exposures offered no benefit to the maize seedlings after stress. Four QTL regions on chromosomes 1, 3, 5 and 7 were well supported with combinations of the phenotype data. Differential expression data from cold stress experiments were used to identify 13 significantly differentially expressed genes within the QTL regions and identify 20 candidate cold memory genes by comparing transcriptomes of trained and untrained plants. These genes potentially explain the difference in response to initial versus secondary cold exposures and cold stress response between B73 and Mo17.

dc_type

text

dc_publisher

DigitalCommons@Hamline

dc_format

application/pdf

dc_source

Departmental Honors Project

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