Gene Mapping And Transcription Analysis Of A Panicle Apical Abortion(sipaa1)in Foxtail Millet

Foxtail millet is an annual crop belonging to Setaria of Gramineae,and also it is the main food crop in the arid and semi-arid regions of northern China,which is commonly known as‘millet'after its seeds are peeled off.Meanwhile,because the content of essential amino acids in millet is higher than that of wheat,corn,sorghum and rice,and the contents of calcium,phosphorus,iron,carotene,and vitamin B are also abundant,it is becoming an important healthy nutrient food.Millet is a diploid monocotyledon C₄ crop,self-pollinated,has a short reproductive cycle?80-140 days?and a relatively small genome?about 515 Mb?and easy to use in the lab.At the same time,based on the high collinearity with the rice genome,foxtail millet has been been proposed as an ideal model for crops research.The panicle is the final expression organization of millet yield,and the morphology and structure of panicle is always an important index of genetic breeding.The panicle apical abortion seriously affects the yield and quality of the crops.What we need to do is to reveal the genetic mechanism of the abortion of the panicle tip to guide the improvement of grain yield and quality by studying the genetic mechanism of the panicle apical abortion.A foxtail millet with panicle apical abortion induced from Yugu1 by EMS treatment,was genetically identified and named as sipaa1.We conducted an agronomic survey of mutant and the result show that the phenotypic variation of the mutant was mainly concentrated on the panicle compared with Yugu1 and the flower at the tip of the panicle developed abnormally,which called‘barren tip'and will result in a sharp drop in grain production.Through genetic analysis,it was found that barren tip is a single gene-controlled trait variation.Therefore,the mutants were genetically mapped using BSA mixed pool sequencing.Gene mapping of the mutant gene was conducted using panicle apical abortion mutant individuals from F₂segregating population of sipaa1×SSR41.Finally,the mutant gene was mapped into genomic region within Indel marker 1-9.23 and Indel marker1-9.322 in chromosome 1,within 100 Kb range.Result of high-throughput sequencing of the mutant sipaa1 and wild-type Yugu1showed that there are six candidate genes with high expression of the spikelet.On the other hand,RNA-Seq showed that there were 2768 up-regulated differentially expressed genes?DEGs?and 507 down-regulated genes in the mutant sipaa1 and wild Yugu1 and up-regulated genes are more than down-regulated genes.Functional enrichment analysis of differentially expressed genes revealed that they exist mainly in biological pathways such as hormone signal transduction,external stress response,plant-pathogen interaction,etc,which suggested that the mutant gene may activate the response of plants to hormones and stress.Finally,two candidate genes that were highly expressed in the panicle and closely related to floral organ development and stress response were identified by combining RNA-Seq datas and gene tissue expression-specific data.The aim of this study was to find the genetic factors associated with panicle apical abortion and will promote the pathway research of panicle apical abortion related in cereal crops.