Characterisation of six α-expansin genes in Gossypium hirsutum (upland cotton)

Abstract.

A genomic library screen and PCR-based strategies were employed to isolate six genes with sequence similarity to a cotton fibre-specific mRNA encoding an α-expansin. α-Expansins are cell wall proteins that facilitate cell wall extension by disruption of non-covalent bonds between wall components. The characterisation and expression analysis of these six novel genes (GhExp1–GhExp6) is described. Four of them (GhExp3- GhExp6) are expressed within multiple tissues of the cotton plant and two (GhExp1 and GhExp2) give rise to transcripts that are specific to the developing cotton fibre. GhExp1 transcripts are highly abundant in the fibre, while transcripts for GhExp2 are detected at a low level. Cotton fibres are highly elongated cells of the ovule epidermis, and we envisage that GhExp1 may play an important role in cell wall extension during development.