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Rose Lab Research Lines

The current projects are:

Characterization of the Plant Cell Wall Proteome ('Secretome')

The plant cell wall/apoplast plays fundamental roles in numerous aspects of plant biology. This is reflected in an ever-growing list of developmental processes and environmental responses that are being associated with wall-localized molecular interactions and signaling pathways.

It is therefore not surprising that a substantial portion of the plant proteome resides in the cell wall/apoplast.  However, the field of cell wall proteomics is far less developed than those of most other plant compartments and organelles, and involves some unique technical challenges.

 

tomato fruit with seedling germination from its interior


 

 

 

 

 

 

 

My lab has been developing new protocols, functional screens and computational tools to characterize cell wall protein populations.

This has resulted in the identification of many proteins whose location in the cell wall is unexpected, based on predicted sequence or annotated function, or with other novel characteristics, and these have led to a number of spin-off projects addressing various aspects of cell wall function.

We have principally targeted two biological processes that are intimately associated with cell wall/apoplast biology:

  1. The assembly, restructuring and disassembly of the wall matrix during fruit development and ripening.
  2. Molecular mechanisms for attack, defense and counterdefense in the apoplast during plant-pathogen interactions, using tomato (Solanum lycopersicum and the oomycete Phytophthora infestans) as a model system.

  3. More information can be found at the SecreTom project website.

The Plant Polysaccharide Cell Wall

Assembly, Modification, Function and Evolution

We are studying the structure and function of the cellulose-xyloglucan network, believed to be the load-bearing component of dicotyon cell walls, as well as the proteins involved in its assembly and modification.

We have identified a new subclass of endo-1,4-β-glucanases (‘cellulases’, from Glycosyl Hydrolase family 9; GH9) with C-terminal extensions that are structurally reminiscent of  cellulose-binding domains (CBDs). While CBDs are common features of microbial cellulase, these are the first reported examples of plant isoforms with such a domain. We showed that the expression of a GH9 isozyme from tomato is associated with both cell expansion and fruit ripening and have characterized the CBD and catalytic domains through domain-swapping experiments with a bacterial cellulase  (Urbanowicz et al., 2007; Urbanowicz et al., 2007).

tomato fruit with seedling germination from its interior


 

 

 

 

 

 

 

 

 

 

 

These studies laid the groundwork for a DOE-funded project to study the molecular mechanisms of cellulose microfibril formation and modification, in collaboration with colleagues in the Biofuels Research Laboratory (BRL) at Cornell, the University of Kentucky and the Donald Danforth Plant Science Center. We have recently also started a collaboration with researchers at CHESS (Cornell High Energy Synchrotron Source) and have developed a novel analytical platform to use high energy X-rays coup to a high precision focusing system to characterize microfibril structures in living plant material. This was described in a recent paper looking at factors that can modulate microfibril crystallinity (Harris et al., 2012).

Future studies will involve a comprehensive study of determinants of crystallinity, including the roles of the GH9 proteins, and the consequence for bioconversion potential.

The Plant Cuticular Cell Wall

Assembly, Modification, Function and Evolution

We have a number of projects studying various aspects of plant cuticle biology, using tomato fruit as a model system.

Studies of a number of tomato mutants (cutin deficient 1, -2 and -3) have demonstrated that the cutin component of fruit cuticles is critically important for resistance to pathogens, while wax constituents are more likely to govern water loss (Isaacson et al., 2009).

A new technique using 3D confocal scanning laser microscopy, coup with tomographic reconstruction has allowed us to visualize the architecture, deposition patterns and micro-structure of plant cuticles (Buda et al., 2009).

We recently identified cutin synthase as a GDSL-motif lipase/hydrolase protein that polymerizes cutin monomers at the cuticle/polysaccharide cell wall interface (Yeats et al., 2012).

tomato fruit with seedling germination from its interior


 

 

 

 

 

 

 



Substantial variation in the cuticle structure and composition have also been profiled in a collection of wild tomato relatives (Yeats et al., 2012). We are now investigating the functional significance of this diversity.

We have recently expanded our study of cuticles to include evolutionary questions and have demonstrated a conservation of cuticle structure and the genetic pathways underlying cuticle biosynthesis in mosses and flowering plants.