Do corn plants self-prime at dusk?

Author:

May, Kyle D

Area of Honors:

Biology

Degree:

Bachelor of Science

Document Type:

Thesis

Thesis Supervisors:

James Homer Tumlinson III, Thesis Supervisor
Katriona Shea, Thesis Honors Advisor

Keywords:

zea mays
green leaf volatile
lipoxygenase
darkshock
jasmonic acid
priming

Abstract:

Green leaf volatile (GLV) emission as a result of abrupt light to dark transitions, termed darkshock, has been previously observed, but its mechanism and physiological importance has yet to be determined. Here we show that three cultivars of Zea mays, Delprim, B73, and W438, respond to darkshock by synthesizing and emitting GLVs within minutes of darkshock. Within the first 15 minutes after darkshock, Z-3-Hexenal is the predominant GLV. During the second 15-minute interval, Z-3-Hexen-1-ol and Z-3-Hexenyl Acetate begin to replace Z-3-Hexenal. During the third 15-minute interval, Z-3-Hexenyl Acetate is the predominant GLV with only trace amounts of the alcohol emitted. Gene expression of two maize lipoxygenases (LOXs), ZmLOX10, a key enzyme in the GLV biosynthesis pathway, and ZmLOX8, a key enzyme in the jasmonic acid (JA) biosynthesis pathway, was examined. ZmLOX10 was present in leaf tissue, but was not induced in response to darkshock. This suggests that LOX10 activity, rather than presence or absence, limits GLV emission. ZmLOX8 transcript levels, on the other hand, are induced after darkshock, but induction trails GLV emission by peaking between 30 and 60 minutes after darkness. The pattern of LOX8 induction suggests GLVs induce LOX8 as they percolate through the leaf before being emitted; yet, LOX8 transcript levels do not translate into measurable JA levels. The question whether the GLV burst after darkshock primes the plant remains undecided as JA levels, the typical telltale of priming, remain unchanged.