Phenotype Observation And RNA-Seq Analysis Of A Loss Of Spikelet Determinacy(lsd)

The development of male and female inflorescences determine maize grain yield, analysis the inflorescence development mechanism is improtant for improving maize production. In this study, we found a loss of spikelet determinacy(lsd) mutant, compared the phenotype differences between lsd and Wild-Type(WT), and analyzed the differentiatial and developmental differences of various meristems on male and female inflorescences, cleared the cytology reason of variation on mutant. Moreover, we also analyzed the transcriptomes of lsd and WT, and predicted the regulatory network of candidate gene for lsd. These results provided an important evidence for lsd involving into regulation of inflorescence development in maize. The main results are as follows:1. Through phenotype identification, we found that lsd and WT have a significant difference in seven phenotypes: plant height、ear height、tassle length、leaf length、leaf width、leaf number above ear and tassel branches. When spikelet-pair meristem(SPM) developed, the process of male and female inflorescence development in lsd began to lag behind, and more severly in female. Interestingly, this phenomenon was more serious with the development of inflorescence.2. The scanning electron microscope results as follows: Compared with WT tassel inflorescence, lsd was wider and longer; lsd branch meristems(BMs) were suppressed, with less or no BM; One lsd SPM differentiated into three spikelet meristems(SMs) rather than two SMs, with one larger in the middle and two smaller on the sides; Moreover, most of lsd SMs showed no differentiaion of floral meristem(FM), and glumes developed abnormally. Compared with WT ear inflorescence, lsd showed a abnormal phnotype from inflorescence meristem(IM) development process, with some were larger, some had two growth cones; lsd SPMs developed more abnormally than tassel, with one SPM differentiated into two or three different SMs; lsd FM and glume are supressed; Ultimately, lsd ear inflorescence showed a variety of phenotypes: some with BMs; some with meristems like leaf; some looked like a flat paper; some splited into two parts on the top; some had a flat and extensive top; some produced two or more growth cones.3. The analysis of transcriptome found that 1063 genes were different expressed in lsd, of which 210 were activated and 853 were suppressed. GO analysis found different expressed genes(DEGs) were enriched in water binding of molecular function、first metabolism and cell metabolism of biological process. Moreover, some DEGs were members of GRF family genes、cell cycle and expansion related genes, inflorescence development related genes、hormone related genes. qPCR confirmed two GRF family genes、four cell cycle genes、five inflorescence development related genes、eight hormone synthesis and signal related genes different expressed in lsd. We hypothesized ZmGIF1, as a transcription factor, may combined with ZmGIF10; Activated the expression of cell cycle and cell expansion-related gene, and promoted cell proliferation. Moreover, Regulated auxin balance by affecting the expression of inflorescence development related genes, such as vt2. Ultimately, the development of inflorescence was influenced.