PJB-2017-525
REGULATORY EFFECT OF SUCROSE SYNTHASE (SUS) AND INVERTASE (INV) ON COTTON FIBER INITIATION FROM OVULE EPIDERMAL CELLS
MUKHTAR AHMED
Abstract
Cotton fiber initiation from ovule epidermal cell occurs from 0-5 days post anthesis (DPA). It is considered that Invertase (INV) and Sucrose Synthase (SuS) are crucial for cotton fiber initiation as these two enzymes catalyze sucrose breakdown into glucose and UDP-glucose which will influx to fiber cell and contribute to its expansion and elongation. Two commercial cotton varieties, Xuzhou 142-normal wild type (WT) and Sea Island PimaS-4 with normal fibers (PimaS-4) were used as controls and compared with three fiber mutants i-e Xuzhou 142-fl without lint and fuzz (fl), Xuzhou 142-N without fuzz (N) and Ligon lintless (Li) with very short fiber about 6~8mm length. SuS, INV activity, sugars and malate content were investigated during fiber cell initiation and early development. While comparing SuS activity at 0DPA with -1DPA it was found that WT, PimaS-4 and Li ovules have respectively 169.05, 154.84, and 68.11% higher SuS activity at 0DPA as compared to -1DPA. However, in fl and N mutants, activity declined from 51.4 to 64.7%. On the other hand, fl mutant has high sucrose content than N and Li cotton ovules during fiber initiation from 0DPA to 1DPA. INV activity was not observed in ovules of all cotton lines from -1DPA to 5DPA. There was a significant difference in total soluble sugars and malate contents between WT and fl cotton ovules at 5DPA only, which depicts that soluble sugar and malate, had no distinct role in fiber initiation, although they might promote early fiber elongation as evident from their elevated level at elongation stage. The results showed that SuS activity at anthesis day determines the fate of ovule epidermal cells to bulge out and form fiber initials. The reduced SuS activity in fl ovules at 0DPA results in a lack of fiber cell initiation and lead to fiberless seed phenotype. The study will pave the way towards unraveling the mechanism of initiation and development of this unique cell by exploration of other factors like phytohormones and genes.
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