Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Dr. Abdelali Hannoufa

Abstract

In Arabidopsis thaliana, carotenoid degradation by enzymatic oxidative cleavage is catalyzed by nine CCD and NCED enzymes; this cleavage produces an array of terpenoid products that are collectively known as apocarotenoids, which include volatile and non-volatile compounds. Previous studies on CCD1 revealed that its overexpression in A. thaliana enhances β-ionone emission and reduces damage caused by flea beetles. In consideration of these findings, I generated CCD4 and CCD8 Arabidopsis overexpression lines. Further, I characterized these overexpression lines on the basis of their carotenoid content and their volatile profiles. Surprisingly, accumulation of key carotenoids in the leaves was observed in both CCD4 and CCD8 plants. In addition, GC-MS analysis indicated that the CCD4 and CCD8 lines showed variable changes in their volatile profiles relative to the control. Varying amounts of volatile apocarotenoids were observed in the CCD4 and CCD8 lines, and none were detected in the WT plants. In addition, there was a presence of other volatile compounds, including sesquiterpenes and monoterpenes, which were present in the transgenic lines; these volatile compounds have been found to be insect feeding deterrents. Further, insect bioassays were conducted using the crucifer flea beetles to determine if the CCD4 and CCD8 plants had enhanced deterrence of insect feeding. The CCD4 lines showed the highest insect feeding deterrence compared to the CCD8 and WT control lines suggesting that the volatile compounds released from these plants possibly had feeding deterrence towards this insect.


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