Biochemistry and Molecular Biology
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More Genes Involved in Petunia Hybrid Vigor

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More Genes Involved in Petunia Hybrid Vigor

Flower of Petunia inflata, a wild species of gardent petunia. Credit: Christopher Natale, BMB Department, Penn State

How does a plant containing both male (stamens with their pollen producing anthers) and female (pistil) reproductive organs in close proximity prevent inbreeding and promote genetic diversity? Through a very clever mechanism that BMB professor Teh-hui Kao and his collaborators have been uncovering in Petunia.

Previously, Kao found the S-RNase gene that directs self-pollen recognition and destruction by its pistil, thus preventing inbreeding. Next was the Type-1 SLF gene whose associated pollen protein inactivates non-self pistil S-RNase proteins. This action ultimately enables seed production of genetically distinct plants.

Recently Kao, together with Seiji Takayama in Japan, discovered 5 new Petunia genes named Type 2 to Type 6 SLF. Overcoming the limited scopes of the Type-1 SLF gene, these expressed genes expand the number of different non-self pistil S-RNase proteins that are detected and degraded. This important finding helps explain the observed extensive genetic diversity and evolution of Petunia.

In the United States, the majority of crops are grown from hybrid seed because such plants have greater vigor and produce higher yield than plants grown from seed obtained from self-pollination. However, almost all crop species are self-compatible because breeders have purposely or inadvertently selected out self-incompatibility in order to produce inbred lines homozygous for desired traits. As a result, to produce hybrid seed of commercial cultivars, it is necessary to manually or mechanically remove anthers from the plant serving as female parent to prevent self-fertilization. This process is labor intensive, costly, and inefficient. Thus, there is a pressing need for more economically advantageous methods for hybrid seed production. Restoration of self-incompatibility back to crop species will greatly facilitate hybrid seed production and produce tremendous agronomic benefits.


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