Scientific questions
Our main scientific interest resides on plant development, more specifically on the mechanism of action of peptide hormones, what are their cellular roles, what are the components of their signaling pathways and what are their effects on the plant physiology and plant development. This line of research started during my post-doctorate (Washington State University, Pullman, WA, USA) where we discovered a new family of peptide hormones in plants that we called RALF, short for “Rapid Alkalinization Factor”. This work was published in 2001 (PNAS v.98, p.12843 – 12847) and, since then, my group is trying to unravel not only the function of these peptides but also their mechanism of action. Two other papers from our group already in Brazil follow: one published in Plant Molecular Biology (73: 271-281) e another in FEBS Letters (582, 3343-3347). They both answer, although partially, questions related to preproRALF processing and also the function of RALF peptides in plants. Regarding the function of the peptides, we found that the RALF peptides regulate the cell expansion, more specifically the cellular elongation.
Current projects
RALF peptides in the plant-pathogen relations
In the model organism Arabidopsis thaliana, some RALF peptides are capable to modulate plant immunity. AtRALF23, for instance, suppresses the immune response by destabilizing the interactions amongst PRRs and co-receptors. AtRALF23 also participates with the jasmonic acid signaling pathway, which suppresses the salicylic acid-induced immune responses. On the other hand, AtRALF17 stimulates plant immunity via unknown mechanisms. Which is the involvement of these peptides in immune responses, or defense, of other plant species is still not known. Some plant pathogens, such as fungi, bacteria, and nematodes, possesses RALF homologs. Such an example is the fungus Fusarium proliferatum, which is capable to infect tomato leaves (Solanum lycopersicum). Our objective is to investigate the involvement of the RALF peptides of F. proliferatum and SlRALF1 and SlRALF2 in this interaction.
RALF peptides in the regulation of stomatal aperture in response to drought stress
Peptide hormones have been implicated in the regulation of signaling processes within the guard cells, either in biotic or abiotic stresses. In the model plant Arabidopsis thaliana, results suggest that the peptide AtRALF1 might be involved in the regulation of stomatal aperture. However, some questions still opened, mainly regarding the mechanism by which these peptides induce changes in the stomatal aperture in response to abiotic stresses. In tomato (Solanum lycopersicum) there are eight RALF peptides (SlRALF). To date, it has not been investigated what are the functions and how these peptides interfere with hormones in abiotic stresses in tomato plants. Thus, our objective is to characterize the RALF-mediated responses to drought stress and how the SlRALF interferes with hormones in these responses.