by Javid.bio-bee

Created on: July 25, 2009

Apomixis is an asexual (agamic) reproduction which results in a progeny that is genetically identical to their parent plant. An alternative to the apomixis is the sexual reproduction or amphimixis. Both the apomixis and the sexual reproduction events take place in the ovule, which is the precedent to the seed. When apomixis is introduced in agronomically important crop plants such as maize, rice etc., farmers could then use the seeds from these plants for successive planting and reduce seed expenses, and maintain high consistent yields. So far, the exact molecular mechanisms underlying the apomictic processes and the genes which govern this phenomenon are not fully known. Therefore, extensive studies on various aspects of the apomixis trait such as the inheritance patterns, chromosomal regions involved, and gene expression profiles associated with the regulation of apomixis have been undertaken by the researchers around the world to understand the mechanism(s) leading to apomixis.

Using the differential display technique researchers were successful in detecting the differentially expressed transcripts between the apomictic and the sexual genotypes. In Panicum maximum, a single cDNA that was specifically expressed in the ovules of apomict was isolated using the cDNA library generated from only the apomictic ovules. In Hieracium, a DEFICIENS homolog was isolated by the differential display of the stage specific transcripts from mature embryo sac, developing embryo and the endosperm. The expression of this homolog of the DEFICIENS was shown to be transiently down-regulated during the initiation of the apomixis in the ovules of apomict Hieracium.

Although, the differential display has been a very useful technique for the isolation of differentially expressed transcripts between the apomictic and its sexual counterpart of many species, there still remain few drawbacks. It demands immense care while staging the ovules for the differential display, because a slight mistake in the staging may miss the important messages whose expression or mis-expression is responsible for the switch in the mode of reproduction. Also, since the differential display makes use of arbitrary primers, the verification of the gene expression of the isolated (differentially expressed) sequences by further nucleic acid or fluorescent hybridization studies becomes essential.

The cDNA-AFLP-analysis approach of the transcript profiling was found to be more effective than the differential

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