| Preliminary studies in the laboratory found that Zm STK1 is a pollen-specific receptor-like protein kinase located in the cytoplasm.Zm STK1 is expressed at the late stage of pollen development,and mutation leads to pollen abortion.However,the expression characteristics of Zm STK1 gene,pollen-specific cis-acting elements and the regulatory mechanism of this gene on maize pollen development are still unclear.In this study,the wild-type Mc C maize tassel was treated with different conditions,and the expression changes of Zm STK1 gene were analyzed by RT-PCR experiments to clarify the expression characteristics of Zm STK1 gene.The transgenic tobacco pollen was observed by GUS histochemical staining,and the core cis-acting elements that determine the pollen specificity of Zm STK1 gene were clearly determined;phenotype,tissue and ultrastructure were observed on the tassel of wild type and Zm STK1 mutants and pollen at different developmental stages to clarify the direct cause of pollen abortion,the research results are as follows:（1）The tassel of Mc C wild-type maize was treated under different conditions,and the subsequent RT-PCR results showed that the expression level of Zm STK1 was basically unchanged under high temperature,drought,methyl jasmonate and salicylic acid treatment compared with the control group;Under high salt and auxin treatment,the expression level showed a downward trend;under abscisic acid treatment,the expression level showed an upward trend.（2）The expression vector of GUS was driven by constructing 5’deletion fragments of the Zm STK1 promoter of different lengths and transformed into tobacco.The staining results showed that GUS activity could be detected in transgenic tobacco pollen by transforming 980 bp and 700 bp promoter fragments,while promoters of other lengths could not drive GUS expression in pollen,presumably located at three positions-501,-435 and-417 The pollen-specific promoter element is a key element that determines the pollen specificity of Zm STK1.（3）The phenotype observation,I2-KI staining,Alexander staining,paraffin section and ultrastructural observation were performed on Mc C wild-type and zmstk1mutant maize.The results showed that the phenotypes of the mutant tassel,spikelet,floret,anther and pollen grain were normal,and the pollen staining showed that there was a lack of storage substances;the structure of each cell layer of the anther wall of the zmstk1 mutant was normal,and the inclusions began to lack at the S11 stage.The results of transmission electron microscopy showed that the tapetum of the pollen sac wall was degraded normally,the vacuole disappearance was delayed at the beginning of the S11 stage,and the starch granules were lacking in the pollen grains in the S12stage,but the accumulation of the pollen wall was no different from that of the wild type.In summary,we determined the effect of different treatment conditions on the expression of Zm STK1 in pollen,preliminarily located the cis-acting element that determines the specificity of Zm STK1 pollen,and revealed that the mechanism of Zm STK1 mutation leading to pollen abortion is that it affects starch particle formation. |
