Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Biology Dept.


Russell R. Johnson

Second Advisor

Judy Stone

Third Advisor

Lynn Hannum


The plant hormone Abscisic acid (ABA) plays a central role in maturation and germination in seeds, as well as mediating adaptive responses to abiotic environmental stresses. ABA induces the expression of many genes, including late-embryogenesis-abundant genes such as HVA1. To elucidate the ABA signaling pathway leading to HVA1 expression, we focus on the bZIP factor TaABF1. Analysis of the interplay between ABA and TaABF1 in the aleurone cells of imbibing cereal grains indicated that the two are not additive in their induction of the HVA1 promoter. A synthetic ABA analog, PBI-51, did not specifically inhibit the effect of exogenous ABA on HVA1 expression while 1-butanol (which inhibits phospholipase D, an early step in ABA perception) did. Furthermore, inhibition of endogenous ABA perception using 1-butanol reduced HVA1 induction by the overexpression of TaABF1. This result suggests that TaABF1 may undergo an ABA-induced posttranslational modification. However, the lack of synergism between ABA and TaABF1 overexpression in HVA1 induction does not support this conclusion. Therefore, our findings indicate that the branch of ABA signaling leading to HVA1 is more complex than previously believed. We propose a model of ABA signaling involving TaABF1 and other putative components that results in the stimulation of ABA-induced genes.


Abscusuc acid, environmental stress, aleurone cells, phospholipase, genes