Cuticle lipid involvement in plant environmental stress tolerance and fruit development
Abstract
The plant cuticle is a heterogeneous lipidic layer that covers the epidermis of the aerial organs of terrestrial plants. The research described here examines the role of cuticle lipids in plant responses to abiotic and biotic stresses and in tomato fruit development. Analysis of cuticle composition in response to water deficit stress demonstrated that Arabidopsis responded to stress by altering cuticle wax and cutin composition and higher order cuticle structure. Cuticle changes were associated with reduction of foliar water loss and cuticle permeability and the abundance of specific cuticle gene transcripts. It is proposed that water deficit-stress induced cuticle production serves as an important component of plant acclimation to drought. Plants also respond to biotic stress by cuticle alteration. Resistant and susceptible cultivars of wheat were shown to differentially alter cuticle permeability and lipid composition in response to infestation by Hessian fly larvae. Changes in permeability were correlated with changes in cuticle lipid amount. Changes in specific cuticle lipids correlated well with the abundance of cuticle-associated gene transcripts. It is proposed that the induction of specific wax constituents and the maintenance of cutin amounts are important components of wheat seedling resistance to Hessian fly infestation. Recent studies have implicated the cuticle as an important determining factor of tomato fruit shelf life. Furthermore, recent research has intimated that cuticle development is regulated alongside other fruit ripening processes. Analysis of cuticle lipid composition of slow or non-ripening tomato fruit mutants that have long shelf life, revealed aberrant cuticle development patterns accompanied by specific compositional changes that may be related to long shelf life. Additionally, the observed cuticle developmental patterns of two of these mutants challenged the notion that these mutants are equivalent in their non-ripening phenotypes. A forward genetics approach was used to identify three tomato mutants, cd (cutin deficient) 1, cd2 and cd3, whose fruit cuticles had severe deficiencies in cutin content and unique, but altered cuticle ultrastructure. Characterization of the mutants revealed surprising alterations in cuticle physicochemical properties including increased cuticle surface stiffness and increased proportions of both hydrophilic and multiply-bonded polymeric constituents. Furthermore, the results indicated a lack of correlation between cutin amount and permeability of the cuticle to water, but implicated cutin as an important determinant of fruit resistance to microbial infection. Several genes have been implicated in Arabidopsis cuticle lipid synthesis. A candidate gene approach revealed that the locus underlying the previously characterized cer8 mutant was allelic to LACS1, one of nine Arabidopsis long-chain acyl-CoA synthetases thought to activate acyl chains. It was also demonstrated that LACS1 has overlapping function with LACS2 in both cutin and wax synthesis. Evidence is presented that LACS1 is a functionally novel acyl-CoA synthetase that preferentially modifies both VLCFAs for wax synthesis, and long chain (C16) fatty acids for cutin synthesis.
Degree
Ph.D.
Advisors
Jenks, Purdue University.
Subject Area
Plant biology
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.