Comparative transcriptomics analysis reveals stage-specific gene expression profiles associated with gamete formation in Allium sativum L.

Commercial cultivars of garlic, a popular condiment, are sterile, making genetic variation and germplasm innovation of this plant challenging. Understanding mechanism of gamete sterility in garlic and their key regulatory networks is therefore important for fertility restoration. In this work, we conducted a detailed phenotypic analysis of fertile and sterile garlic genotypes and found that enlargement of topset in the inflorescence of sterile genotypes led to abnormal flowers. Additional cytological observations showed that aberrant meiotic cytokinesis in sterile garlic ultimately resulted in pollen degeneration. Transcriptomics analysis of sterile and fertile genotypes identified possible molecular mechanisms underlying gamete abortion. A total of 100 710 differentially expressed genes (DEGs) between the fertile and sterile garlic flowers at three stages of gamete development were identified, many of which were involved in homologous chromosome synapsis during meiosis, MYB transcription factor regulation, ribosome biogenesis and plant hormone signal transduction. Taken together, these results provide insight into the molecular mechanisms and regulatory networks underlying gamete development in garlic and point to a set of candidate genes for further functional characterization.