Effects Of Down-regulation Of GhDET2, A Steroid 5α-reducase Gene Of Cotton, On The Growth And Development Of Cotton (Gossypium Hirsutum L.)

Cotton,one of the most important fiber crops in the world,is a mainstay of economy in China.With the advantages of overcoming genetic obstacle among species and transfer target genes purposively and rapidly,gene engineering provides an effective strategy to improve the yield and quality of cotton fiber.Until now,few genes are found exactly related to fiber yield and quality,which become the main problem for gene engineering in cotton improvement.Phytohormones control numerous aspects of plant growth and development. Brassinosteroids(BRs) are essential for normal organ elongation,vascular differentiation,male fertility,timing of senescence and leaf development.It was also found that BRs promoted flowering early,photosynthetic efficiency and fruit setting, boll enlargement and root development when being applied on cotton.However, exogenous application is not viable in pactice because of high fee and potential environment problem.Gene engineering provide a way to modified levels of BRs in cotton,which could help us elucidate the role of BRs during cotton development and improve cotton properties.A steroid 5α-reducase gene(GhDET2) of cotton,cloned previously in our lab,is required for fiber initiation and elongation.However more details of the GhDET2 in cotton plant growth have not yet known.In this paper,the effects of 35S-driven antisenseGhDET2 on cotton plant development was further studied.The main result are as following:1.The suppression construct of 35S:antiGhDET2 was introduced into cotton genome by Agrobacterium-mediated transformation.Six independent transformants transgenic plants were obtained.RT-PCR analysis revealed that expression of GhDET2 was dramatically depressed in line AD4.2.Morphological comparisons between transgenic plant AD4 and wild-type illuminated that the transgenic plants were severe dwarfed with decreased apical dominance during plants development.No vegetable branches and fruiting branches appeared in transgenic cotton.Moreover,transgenic cotton bolls grew directly from nodes of the main stem.Floral organs such as bracts,petals and stigmas were smaller than that of wild-type.Comparing to wild-type,transgenic plants had less and shorter lateral roots with shorter root hairs.3.Lower density of fiber initials on ovules was obversed in CaMV35S:antiGhDET2 plants on the day of anthesis compared with wild-type.100-seed weight of transgenic plants was 10.55±0.25 g,representing 9.9%lower than wild-type.