Table I.

Fiber growth characteristics, cellulose content, and α-tubulin protein content

Fiber Characteristic10 DPA12 DPA14 DPA16 DPA18 DPA20 DPA
Dry mass (mg/ovule)0.841.5014.4141.769.771.9
Length (cm) 1.5 ± 0.27 1.9 ± 0.33 2.3 ± 0.43 2.7 ± 0.48 2.9 ± 0.48 3.5 ± 0.44
Cellulose content (%)11.9 ± 3.6913.5 ± 2.0214.4 ± 1.9941.7 ± 14.361.7 ± 15.571.9 ± 15.4
α-Tubulin protein accumulation (%)12.7 ± 3.4 36.5 ± 9.8 63.3 ± 17.186.5 ± 23.395.7 ± 12.8100 ± 6.2 

Fiber length was measured for two sets of 20 ovules randomly selected from the same population of cottonseed used for RNA isolation. After length measurement, fibers were stripped from the seed and lyophilized to constant weight. Fiber samples were stored over phosphorus pentoxide prior to weight determinations and cellulose measurements. Replicate fiber samples were hydrolyzed with acetic-nitric reagent, followed by cellulose determination with anthrone. Avicel cellulose (PH-101, FMC) was used as the standard in the cellulose assays. The relative amount of α-tubulin protein was measured by scanning triplicate western blots of equal amounts of total fiber protein isolated from selected stages of development and probed with an antibody YOL 1/34 to α-tubulin. Protein values are expressed as the percentages of the highest protein content in the series.