Functional Analysis Of GhSPO11-3,a Cotton Gene Regulates Endoreduplication,response To Abiotic Stress

SPO11-3 protein is one of the topoisomerase VIA homologues of eukaryotic,and participates in the regulation of important biological functions such as growth,development and stress responses.This experiment was based on the previous results:the silencing of GhSPO11-3 resulted in a failure of cell endoreduplication and led to a phase shift in the levels of ploidies associated with dwarf phenotype.Phenotypically,the down-regulation of GhSPO11-3 led to transgenic plants being more sensitive to salt stress.Here,the virus-induced gene silencing?VIGS?and over-expression?OE?were used to investigate the biological function of GhSPO11-3in G.hirsutum and Arabidopsis respectively.These results indicated that GhSPO11-3likely positively affects plant growth and salt tolerance in G.hirsutum.The results of the study are as follows:1.To analyze the role of GhSPO11-3 in abiotic stress,we examined transcriptional regulation of GhSPO11-3 after treatment of cotton leaves with NaCl,Mannitol,ABA,and H₂O₂ for various lengths of time.qRT-PCR showed that expression of GhSPO11-3 was significantly up-regulated after these stress treatments.These results indicated that GhSPO11-3 may be involved in the response to different phytohormones and stresses,and may also play an important role in the crosstalk between multiple stress responses.2.Virus-induced gene silencing of GhSPO11-3 compromised the tolerance of cotton plantlets to drought stress and reduced the post-rewatering water recovery survival rate as compared with the the wild type?WT?.The higher water loss rate and lower relative water content were detected by the silencing of GhSPO11-3.In addition,the silencing GhSPO11-3 decreased proline,soluble sugar,Chl content as well as antioxidant enzyme activities and increased malondialdehyde?MDA?content in cotton under drought stress.These results further proved that GhSPO11-3 plays essential role in the adaptation of plants to abiotic stresses.3.We found that the transgenic plants accelerated both leaf and root growth accompanied by increased cell expansion and elevated ploidy.For further investigation,transgenic Arabidopsis with overexpression of GhSPO11-3 exhibited a more developed root hair system.In addition,the transgenic plants also showed delayed flowering which prolonged the vegetative growth stage of the plant.4.Overexpression of GhSPO11-3 in transgenic Arabidopsis improves salt and drought tolerance.In response to drought and salt stress,transgenic Arabidopsis plants overexpressing GhSPO11-3 showed significantly higher germination rates,longer roots,and more vigorous growth than wild-type plants.Furthermore,stomatal density and the rate of opening of stomata were markedly decreased in transgenic Arabidopsis.The transcript levels of the antioxidant genes CAT,POD and SOD and stress-responsive genes were generally higher in GhSPO11-3-overexpressing Arabidopsis than in the WT under salt and drought stress.