Analysis of the Protein Constituency of Developing Cotton Fibres

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Abstract
Graves, D. A. and Stewart, J. McD. 1988. Analysis of the protein constituency of developing cotton fibres.—J. exp. Bot. 39: 59–69. Protein composition of young cotton (Gossypium hirsuium L.) ovules and fibres was examined in order to characterize gross changes during early development and to determine if changes correspond to known developmental events. Major emphasis was on the fibre, although ovule development was considered at earlier ages. Ovules and fibres from upland cotton (‘Deltapine 61’) were collected at 6, 3, and 1 d pre-anthesis, at anthesis and at 2, 6, 10, 16 and 20 d post-anthesis. Total protein was extracted from whole ovules or isolated fibres and subjected to two-dimensional gel electrophoresis. The gels indicated the following: (1) The protein patterns of ovules and fibres 3 d pre-anthesis to 2 d post-anthesis were relatively similar, suggesting a plateau in protein expression. The plateau was proposed to reflect the time during which fibre cells are differentiated from other epidermal cells. (2) The plateau was delineated by apparent periods of increased complexity in the population at 3 d pre-anthesis and 2 d post-anthesis. (3) A transition in the protein population occurred between 2 and 10 d post-anthesis. (4) By 6 to 10 d post-anthesis, the fibre began to express proteins putatively involved with secondary wall synthesis. (5) Increases in spot intensity of certain proteins around 16 d post-anthesis may correlate with cellulose synthesis reported by others to peak about this time. These observations suggest that early ovule and fibre development is characterized by at least two distinct protein populations. The first occurs around anthesis and the second occurs by 10 d and extends to 20 d post-anthesis and beyond.