Location: Children's Nutrition Research CenterTitle: H+-PPase AVP1 is necessary for phloem development in Arabidopsis Author
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2012
Publication Date: 5/16/2012
Citation: Paez-Valencia, J., Patron, A., Sanchez-Lares, J., Furstenau, T., Hilton, M., Sanchez-Gomez, C., Valencia-Mayoral, P., Ayre, B., Hirschi, K.D., Gaxiola, R.A. 2012. H+-PPase AVP1 is necessary for phloem development in Arabidopsis [abstract]. Proceedings of the 4th Pan American Plant Membrane Biology Workshop, May 16-20, 2012, Asilomar, California. p. 19. Interpretive Summary:
Technical Abstract: The presence of a plasma membrane (PM) localized type I H+-PPase in sieve elements of Ricinus communis was documented years ago. Unfortunately, the physiological and developmental relevance of these findings remained obscure due to the lack of genetic and molecular reagents to study Ricinus communis. The availability of H+-PPase gain and loss-of-function mutant alleles in Arabidopsis thaliana makes this plant an attractive genetic model to address the functional relevance of this PM localization. We have recently documented that in Arabidopsis thaliana, as in R. communis, the type I H+-PPase AVP1 localizes to the PM in sieve elements and companion cell complexes. Here we present immunohystochemical, ultra-structural and genetic data that document the distribution and potential function of AVP1 in phloem cells. The analysis of two different mutant alleles (avp1-1 and avp1-2) further emphasizes the key role of AVP1 in phloem development. The avp1-1 mutant contains a T-DNA insertion in the fifth exon of the coding sequence, rendering a bona fide loss-of-function allele with a dramatic developmental phenotype. Of significant note, phloem development in these avp1-1 mutants is aberrant. The avp1-2 allele harbors a T-DNA insertion -756 bp upstream from the ATG in the AVP1 promoter. These plants do not show any obvious deleterious phenotype. Immunohystochemical and ultra-structural data show that the topological distribution of AVP1 at the plasma membrane of sieve elements and companion cell complexes is similar to WT plants and that phloem development is intact. However, AVP1 was completely absent from parenchyma cells. These data suggest that the main role for AVP1 in Arabidopsis is at the vasculature. Furthermore, the expression of a phloem specific AVP1:RNAi chimera in an avp1-2 background phenocopied the avp1-1 allele. The ultra-structural and genetic evidence presented here suggests that AVP1 plays a key role in phloem development and maintenance in Arabidopsis. Its absence results in premature cell death of phloem cells, with a dramatic impact in plant development. We will present phenotypic and ultra-structual characterization of genetic-engineered chimeras with tissue-specific expression of AVP1 and the yeast invertase suc 2. These chimeras should shed light regarding the physiological role that AVP1 plays in phloem development.