Analysis Of Imazethapyr Induced Male Sterility In Pepper(Cupsicum Annuum L.)

Pepper(Capsicum annuum L.)is one of the important vegetables in China,it has obvious heterosis in pepper breading.In compared with traditional method of cross breading,it has great advantages to produce hybrids by chemical hybridization agents.Here we apply imazethapyr as chemical hybridization agent to study the effects and mechanism of imazethapyr-induced male sterility in pepper,a cultivar of p70.Here we draw the conclusions as below:1.we chose the concentration of 15 mg/L imazethapyr to induce male sterility in pepper,at this concentration,anthers can show completely male sterility,and imazethapyr induces plant damage at a relative low level.2.We find that male sterility induced by imazethapyr at microspore mother cell stage though performing anther staining and paraffin sections.At the microspore mother cell stage,the inner tapetum cells in the untreated anthers degrade to provide nutrients for microspore mother cells growth and development,while inner tapetum cells in the treated anthers still keep intact without any degradation,which induce the failure of providing nutrients for microspore mother cells,and eventurely the microspore mother cells can not develop into tetrads and then degrade.In addition,Imazethapyr can also induce abnormalities in cell differentiation and delayed degradation of outer tapetum cells in treated anthers,which aggravate male sterility in anthers.3.Under transmission electron microscopy,we observe many autophagosomes in the inner tapetum cells of untreated anthers compeared to the treated anthers,indicating autophagy activities in cells,which will result in cell autophagy death.At microspore mother cell stage,microspores begin to degrade with some autophagy bodies in the vacuoles,and show deformed in shape without enough callose circled around,some organelles include nucleus degrade or vanish in cells.However,in the untreated anthers,microspore mother cells are round,larg,plump and surrounded with abundant callose deposited on the surface.At tetrad stage,microspore mother cells in the untreated anthers undergo meiosis and form into tetrads.However,in thetreated anthers,microspore mother cells can not form into tetrads and degrade,leaving a mixture of organelles and cytoplasm adhere together in the cells.4.we did some gens expression analysis,the gens,ATG8s(ATG8a,b,c,d,e)which are related to autophagic activity,and pec which is related to degradation of cell wall,observing that gens including ATG8 a,ATG8e and Pec have a relative high expression level in the untreated anthers at microspore mother cell stage,this result is closely related to autophagy activities and cell wall degradation in the inner tapetum cells of untreated anthers at this stage;And the gens ATG8 b,ATG8 and ATG8 d have a relative high expression in the treated anthers,which may related to the autophagy activities in the microspore mother cells.The abnormal expression of gens such as EMS,CLV1 and BAM may be related to the abnormal changes in the early stage of the anther,showing decreaed in the number of microspore mother cells and defective anthers.