Molecular Basis of Self-Incompatibility in Petunia

Project: Research project

Project Details



PI: Teh-hui Kao

Petunia inflata possesses gametophytic type self-incompatibility which is

controlled by a polymorphic locus, the S-locus. Matching of S-alleles

carried by the pollen and pistil results in inhibition of pollen tube

growth in the style. A polymorphic gene at the S-locus, termed the S-RNase

gene, that controls pistil function in SI has been identified. However, the

gene that controls pollen function in SI interactions, termed the pollen

S-gene, has not been identified.

The goal of this proposed project is to use a functional genomic approach

to identify the pollen S-gene of P. inflata. Obj. I is to use 14 cDNA

markers for the S-locus and the S-RNase gene as probes to isolate clones

from an S2S2 BAC library already contsructed. Obj. II is to construct a BAC

library of the S1S1 genotype and use the same probes employed in Obj. I to

isolate positive clones. Obj. III is to characterize all the BAC clones

isolated in Obj. I and II by pulse-field gel electrophoresis and

fluorescence in situ hybridization to determine any overlap between them,

to order them at the S-locus, and to estimate the size of the gaps between

them. Additional clones will be isolated from both BAC libraries to cover

as extensively as possible the entire S-locus. Obj. IV is to introduce all

the BAC clones separately into P. inflata plants of S1S2 genotype to

determine whether any of them contains the pollen S-gene. If a BAC clone

contains the pollen S2-gene, a quarter of the pollen grains produced by a

transgenic plant will carry the pollen S1-allele and the pollen

S2-transgene, and they will be compatible with S1S2 pistils due to

competitive interaction. Transgenic plants that have become

self-compatible will be studied to identify the transgene that is

responsible for the phenotype. The function of the candidate(s) for the

pollen S-gene will be further ascertained by loss-of-function experiments.

Accomplishment of this proposed research will advance the understanding of

an RNase-based self/non-self recognition mechanism. The BAC clones isolated

can be used for studying the functions of additional S-locus genes, and for

comparative study of the S-locus of two different S-haplotypes, S1 and S2.

On the practical side, one can explore the possibility of restoring the SI

trait to self-compatible cultivated species to facilitate hybrid seed

production. If successful, this will have a very important agronomic


Effective start/end date4/1/003/31/04


  • National Science Foundation: $396,000.00


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