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

Garlic is globally cultivated and consumed as a condiment and vegetable crop, and is also utilized for its nutraceutical benefits. However, a lack of sexual reproductive capability reduces genetic variation and germplasm innovation in commercial cultivars of garlic. Recent studies in fertility restoration of bolting genotypes have resulted in successful flowering and seed production, thereby enabling genetic research and conventional breeding in garlic. In this work, we conducted 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 and ribosome biogenesis. Taken together, these results provide insight into the molecular mechanism and regulatory networks underlying gamete development in garlic and identify a set of candidate genes for further functional characterization.