Functional Analysis Of ZmEG1 Gene In Spikelet Development

Maize (Zea mays) has become an excellent model organism for studying the sex determination and spikelet development of plants. Different from rice with bisexual-flowers development process, maize is a monoecious plant which forms mature separate male and female flowers on separate tassel and ear inflorescences, respectively. To date, the maize genome has been sequenced. while, the annotation of genes function is still underway. Thus, it is particularly important to reveal the function of floral genes by reverse genetic methods.OsEG1 is an important spikelet meristem gene regulating floral meristem determinacy and floral organ differentiation. It encodes a phospholipase A1.OsEGl can affect the organ development of rice spikelets by participating in jasmonic acid (JA) biosynthesis process. Maize bears two kinds of inflorescence, male (tassel) and femal inflorescence (tassel).In order to study the function of ZmEG1 gene in maize and to explore whether EG1-like protein has divergent function during evolution, bioinformatics was used for analysing ZmEG1 gene promoter and the encoded protein in this study. Moreover, the light microscopy, SEM, TEM paraffin and Q-PCR were used for observing the overexpression ZmEG1 transgenic rice phenotype, anatomical structure and gene expression. The results showed that the function of ZmEG1 gene is conservative, as meristem gene regulated spikelet organ morphgenesis, with OsEG1 gene. It is also an important gene that deternimed male fertility. The main results of this research are summarized as follow:1. Bioinformatics analysis shows that ZmEG1 promoter contains MeJA-response element. Comparative amino acid sequence indicates that ZmEGl has same lipase conserved sequence GXHXG-motif with OsEG1,AtDGL, AtDAD1 and the catalytic triad in enzyme active center are serine, aspartic and histidine. indicating ZmEG1 gene encoding the lipase belongs to PLA1. ZmEGl is similar to OsEGl of rice with homo logy proportion 76.48%2. This study shows that floral organs morphology and numbers have changed in the ZmEG1 transgenic rice. SEM and paraffin section observation suggest that floral organ primordia is abnormal differentiation and losses meristem determinacy. Eventually it leads to abnormal differentiation of floral organ. Q-PCR expression analysis shows that ZmEGl regulates expression of the formation of floral organ genes. Studies show that ZmEGl is involved in the development of rice spikelet meristem and the function of ZmEGl gene is conservative with OsEGl gene.3. The stamen is complete male sterile in rice with ZmEGl overexpression. Paraffin observation suggests that the anther wall cells abnormal developed in ZmEGl transgenic rice. The degradation of wall cellular stops and becomes larger, chamber becomes smaller, squeezes microspore and deformative, anther indehiscence, leading to pollination failure. This observation strongly indicates that ZmEG1 gene is one of the major regulatory steps in the anther development. SEM and TEM observation suggest that the anther wall contains a large number of starch granules, so that influences the formation of mature microspore and lead to microspore abortion. The results show that ZmEGl, as a lipase gene, affects the fertility of stamen in transgenic rice. Q-PCR expression analysis shows that the genes expression related anther development have a significant change. These genes are involved in JA biosynthesis or signal transduction. These results indicate that ZmEGl gene may be related to JA biosynthesis or signal transduction.