Molecular analysis of interacting abscisic acid signaling effectors in protoplasts

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Title: Molecular analysis of interacting abscisic acid signaling effectors in protoplasts
Author: Gampala, Satyalinga Srinivas
Abstract: Abscisic acid (ABA ) is a plant hormone that plays an important role in growth and development , regulation of seed maturation , germination , and adaptation to environmental stresses . ABA signaling pathways overlap with other signaling pathways such as hormone - , developmental - , sugar - , and stress -response pathways suggesting a complex network of interactions . Although physiochemlcal and molecular genetic approaches have provided fundamental insights into ABA signaling , our knowledge about transcriptional regulation of ABA signaling and components required for ABA signal transduction is far from complete . I have taken a multidisciplinary approach involving biochemical , molecular , genetic and pharmacological techniques to characterize ABA signaling in protoplasts . I have developed and utilized transient gene expression in protoplasts to functionally analyze the interactions of ABA regulatory genes {ABA INSENSITIVE -1 , -3 and -5 -Like gene families ) . Using a pharmacological approach , I demonstrated that phospholipase D (PLD ) functions in ABA -inducible gene expression in rice . Antagonism of ABA , VIVIPAR0US1 (VP1 ) and lanthanum synergy by 1 -butanol , a specific inhibitor of PLD , was similar to the inhibition by co -expression of ABI1 -1 . These results have shown that ABA , VP1 , lanthanum , PLD and ABM are all involved in ABA -regulated gene expression and are consistent with an integrated model whereby La^"" acts upstream of PLD . Using transient gene expression in rice and maize protoplasts , I have shown that overexpressed ABI5 transactivates several ABA -inducible promoters from both monocots and dicots and synergizes with ABA and co -expressed VP1 . ABI5 also interacted with other known ABA signaling effectors such as ABU , lanthanum and PLD to regulate ABA -inducible gene expression demonstrating that ABI5 is a key target of a conserved ABA signaling pathway in plants . Based on my results , I propose that overexpression of ABI5 -Like family members in combination with VP1 will confer value -added traits to transgenic plants including drought and salt tolerance , viability under stress and tissue -specific target gene expression . Reverse genetic analysis of ABF3 , a member of the ABI5 -Like family , demonstrated that ABF3 mutants are insensitive to ABA -inhibition of root growth confirming the role o1 ABF3 in vegetative ABA responses . Regulation of ABA signaling by post -transcriptional mRNA processing is discussed .
URI: http : / /hdl .handle .net /2346 /21620
Date: 2004-05


Molecular analysis of interacting abscisic acid signaling effectors in protoplasts. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /21620 .

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