29 research outputs found
Ultrastructural features of Mimulus aurantiacus (Scrophulariaceae) pollen tubes in vivo
Evolutionary Genetics of an S-Like Polymorphism in Papaveraceae with Putative Function in Self-Incompatibility
Papaver rhoeas possesses a gametophytic self-incompatibility (SI) system not homologous to any other SI mechanism characterized at the molecular level. Four previously published full length stigmatic S-alleles from the genus Papaver exhibited remarkable sequence divergence, but these studies failed to amplify additional S-alleles despite crossing evidence for more than 60 S-alleles in Papaver rhoeas alone.Using RT-PCR we identified 87 unique putative stigmatic S-allele sequences from the Papaveraceae Argemone munita, Papaver mcconnellii, P. nudicuale, Platystemon californicus and Romneya coulteri. Hand pollinations among two full-sib families of both A. munita and P. californicus indicate a strong correlation between the putative S-genotype and observed incompatibility phenotype. However, we also found more than two S-like sequences in some individuals of A. munita and P. californicus, with two products co-segregating in both full-sib families of P. californicus. Pairwise sequence divergence estimates within and among taxa show Papaver stigmatic S-alleles to be the most variable with lower divergence among putative S-alleles from other Papaveraceae. Genealogical analysis indicates little shared ancestral polymorphism among S-like sequences from different genera. Lack of shared ancestral polymorphism could be due to long divergence times among genera studied, reduced levels of balancing selection if some or all S-like sequences do not function in incompatibility, population bottlenecks, or different levels of recombination among taxa. Preliminary estimates of positive selection find many sites under selective constraint with a few undergoing positive selection, suggesting that self-recognition may depend on amino acid substitutions at only a few sites.Because of the strong correlation between genotype and SI phenotype, sequences reported here represent either functional stylar S-alleles, tightly linked paralogs of the S-locus or a combination of both. The considerable complexity revealed in this study shows we have much to learn about the evolutionary dynamics of self-incompatibility systems
Quantitative proteomics of the tobacco pollen tube secretome identifies novel pollen tube guidance proteins important for fertilization
The transmitting tissue of Nicotiana tabacum is not essential to pollen tube growth, and its ablation can reverse prezygotic interspecific barriers
Structure and function of class III pistil-specific extensin-like protein in interspecific reproductive barriers
Microtubule associated protein WAVE DAMPENED2-LIKE (WDL) controls microtubule bundling and the stability of the site of tip-growth in Marchantia polymorpha rhizoids
Identification of the Pollen Self-incompatibility Determinant in Papaver rhoeas.
Higher plants produce seed through pollination, using specific interactions between pollen and pistil. Self-incompatibility is an important mechanism used in many species to prevent inbreeding; it is controlled by a multi-allelic S locus1,2. ‘Self’ (incompatible) pollen is discriminated from ‘non-self’ (compatible) pollen by
interaction of pollen and pistil S locus components, and is subsequentlyinhibited. In Papaver rhoeas, the pistil S locus product is a small protein that interacts with incompatible pollen, triggering a Ca21-dependent signalling network, resulting in pollen inhibition and programmed cell death3–7. Here we have cloned three alleles of a highly polymorphic pollen-expressed gene, PrpS (Papaver rhoeas
pollen S), from Papaver and provide evidence that this encodes the pollen S locus determinant. PrpS is a single-copy gene linked to the pistil S gene (currently called S, but referred to hereafter as PrsS for Papaver rhoeas stigma S determinant). Sequence analysis indicates
that PrsS and PrpS are equally ancient and probably co-evolved. PrpS encodes a novel 20-kDa protein. Consistent with predictions that it is a transmembrane protein, PrpS is associated with the plasma membrane. We show that a predicted extracellular loop segment of PrpS interacts with PrsS and, using PrpS antisense oligonucleotides, we demonstrate that PrpS is involved in S-specific inhibition of incompatible pollen. Identification of PrpS represents a major advance in our understanding of the Papaver self-incompatibility system. As a novel cell–cell recognition determinant it contributes to the available information concerning the origins and evolution of cell–cell recognition systems involved in discrimination between self and non-self, which also include histocompatibility systems in primitive chordates
and vertebrates