Expression of recombinant S-locus F-box-S2 protein and computational modeling of protein interaction at the self-incompatibility locus of Rosaceae
Loading...
Date
2012
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Self-incompatibility (SI) is a major mechanism that prevents inbreeding in
ow-ering plants, which was identi ed in Rosaceae, Solanaceae and Scrophulariace.
In these families, SI is gametophytic and retains inter-speci c genetic variations
by out-crossing promotion. Self-incompatibility is genetically controlled by an S-
locus where both male (pollen) and female (pistil) S-determinants are encoded.
The female determinant (SRNase) has been extensively studied, whereas its male
counterpart (SLF/SFB) has only recently been characterized as a pollen-expressed
protein, which encodes for an F-box domain. However, the exact mechanism of in-
teraction between SLF/SFB and SRNase is still largely unclear in Rosaceae. This
study takes a closer look at the mechanism of self-incompatibility to gain a clearer
understanding of the ligand-receptor binding mechanism of SI using molecular
evolutionary analysis, structure prediction and binding speci city characteriza-
tion, the outcome of which, will translate into a guideline for future studies. The
major aims of this study were to derive an evolutionary pattern for GSI in Rosaceae
subfamilies and to further assess the collaborative non-self recognition in Malus
domestica Borkh.. The evolutionary analysis suggests a di erence in the evolution-
ary pattern of Prunoideae and Maloideae S-genes, hence proposing a di erence in
their GSI systems. Furthermore, sites responsible for this divergence are identi ed
as critical amino acids in GSI function. To maintain GSI it is expected that the
S-genes must be linked and co-evolve as a genetic unit. The results of this study
show that these genes have co-existed, while SRNase have experienced a higher
rate of evolution compared to SLF, thus rejecting the co-evolution of these genes
in Maloideae. Furthermore, positively selected sites of S-locus pistil and pollen
genes were identi ed that are likely to be responsible for speci city determination.
Di erent numbers of these sites are found for both S-genes, while SRNase holds
a larger number of positively selected sites. Additionally a model of speci city
is introduced that supports the collaborative non-self recognition in Malus GSI,
while critical sites responsible for such speci city are proposed and mapped to the
predicted ancestral tertiary structure of SRNase and SLF/SFB. The identi cation
of regions determining pollen pistil speci city as well as proposing a Collaborative
Non-self Recognition model for Malus domestica Borkh. provide greater in-sight into how pollen-pistil communication system works in Maloideae (Rosaceae
subfamily).
Description
Philosophiae Doctor - PhD
Keywords
Self-incompatibility (SI), Solanaceae and Scrophulariace, The female determinant (SRNase)