Expansins are proteins that mediate cell-wall loosening and are regulators
of wall extension during plant cell growth. However, limited information is
available on their precise biological functions in plant growth and
development. Previous transcriptome analyses suggest that expansin genes
play an active role in seed development and yield. In this study, a sweet
potato expansin gene (IbEXP1) was overexpressed in Arabidopsis to determine
the effect of the expansin gene in seed development and yield in
heterologous plants.

The growth rate was enhanced in IbEXP1-overexpressing plants relative to
wild-type plants during early vegetative growth stage. More rosette leaves
and thicker siliques were observed in transgenic plants than in control
during reproductive stage. Transgenic plants also produced larger seeds and
accumulated more protein and starch in seeds. Transgenics also produced more
inflorescence stems and siliques than wild-type plants, leading to higher
total seed yield per plant.

The results showed the favorable effect of the overexpression of IbEXP1 gene
on seed size and seed number in heterologous plants. The improvement of
these two phenotypes directly leads to a better seed yield.

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