Effect Of Light Treatments On Cotton Hypocotyls Inducing Somatic Embryogenesis

Cotton tissue culture began in the1970s. Price and Smith firstly inducted somatic embryo fromGossypium klotzschianum L in1979， but not get regeneration plant. Daviddonis fistly obtainedregeneration plant from Coker312callus cultured for more than two years in1983,and this recalled theinterests of cotton researchers’s. Shoemaker reported the regeneration of Coker312and201subsequently.Then, numerous cotton researchers at home and abroad not only induced somatic embryosbut also got regeneration plants from different cotton species.And some cotton researchers found explantsgot from different sources have a different ability in inducting somatic embryo. Physiological metabolismand low differentiated tissue is advantageous to the induction of somatic embryogenesis,generally.Objective：Xinluzao33、Xinluzao45、Xinluzao50and Coker312which used as experiment materials werecultured in differrnt light cycles,and hypocotyls of aseptic seeding were uesd as experiment explants andcultured as materials of paraffin section to observe morphology of cells changing. GhSERK1、GhLEC1were select to study the realative expression in different hypocotyls cultured in different light cyclessubsequently.This two methods both have the same goal to get a suitable light cycle for cotton culture, sothat to serve favourable explants for cotton tissue culture and cotton genetic transformation experiment.Method： Xinluzao33、Xinluzao45、Xinluzao50and Coker312were cultured under four light cycles【a: Dark treatment for6d;b: Dark treatment for3d and light treatment for3d;c: Dark treatment for12hand then light treatment for12h,cultured for6d;d: light treatment for6d;】 treatment as experimentmaterials. Hypocotyls of aseptic seeding cultured for0d、3d、7d in callus induction medium were uesd asmaterials of paraffin section to observe morphology of cells changing. GhSERK1、GhLEC1were select inreal time PCR experiment to study the effect of different light treatments in realative expression indifferent hypocotyls subsequently.Result：Paraffin section of hypocotyls after light cycles treatment cultured on callus induction medium for0d、3d、7d showed that there is almost no difference in cell morphology of hypocotyles cultutre for0d afterlight cycles treatments; cells of hypocotyles cultutre for3d in primary mertstem wrer quicker proliferationunder light cycle b treatment; meristem cell masses in outer-cortex were observed in four cottonhypocotyles cultutre for7d; in primary mertstem and outer-cortex, meristem cell masses of Xinluzao45were observed under light cycle b and light cycle c treatment;for coker312, meristem cell masses inprimary mertstem and outer-cortex were observed under four light cycles treatment.RT-PCR result showedthat the expression of GhSERK1、GhLEC1was relatively higher under light cycle b treatment, compariedwith other treaments.For coker312, the expression of GhSERK1was relatively higher comparied withXinluzao33、45and50.Conclusion：These results indicated that the treatment of dark treatment for3d and light treatment for3d ismore advantage for cotton callus induction and the expression of gene GhSERK1、GhLEC1. Meristem cell masses mainly originated in primary mertstem under the hormone combination of2,4-D+KT.The genotypeis a key factor limiting cotton somatic embryogenesis.