Mutation in BrGGL7 gene encoding a GDSL esterase / lipase causes male sterility in Chinese cabbage (Brassica rapa L. ssp. pekinensis)

Cloning and functional verification of the male sterile gene BrQRT3 in Chinese cabbage

Chinese cabbage is a cross-pollinated crop with significant heterosis, and male sterile lines are an important way to produce hybrid seeds. In this study, a male sterile mutant msm0795 was identified in an EMS-mutagenized population of Chinese cabbage. Cytological observations revealed that the microspores failed to separate after the tetrad stage, and thus developed into abnormal pollen grains, resulting in anther abortion. MutMap combined with Kompetitive Allele Specific PCR genotyping showed that BraA01g011280.3.5 C was identified as the candidate gene, which encodes polygalacturonase QRT3 and plays a direct role in the degradation of pollen mother cell wall during microspore development, named BrQRT3. Subcellular localization and expression analyses demonstrated that BrQRT3 was localized in the cell membrane and was ubiquitously expressed in roots, stems, leaves, flower buds, and flowers, but the expression of BrQRT3 was gradually suppressed with the anther development. Ectopic expression confirmed that over-expression of BrQRT3 in qrt3 background Arabidopsis mutant can rescue the pollen defects caused by loss of AtQRT3 function. It is the first time to achieve a male sterile mutant caused by the mutation of BrQRT3 in Chinese cabbage. These findings contribute to elucidate the mechanism of BrQRT3 in regulating stamen development of Chinese cabbage.

Genome-Wide Classification and Phylogenetic Analyses of the GDSL-Type Esterase/Lipase (GELP) Family in Flowering Plants

GDSL-type esterase/lipase (GELP) enzymes have key functions in plants, such as developmental processes, anther and pollen development, and responses to biotic and abiotic stresses. Genes that encode GELP belong to a complex and large gene family, ranging from tens to more than hundreds of members per plant species. To facilitate functional transfer between them, we conducted a genome-wide classification of GELP in 46 plant species. First, we applied an iterative phylogenetic method using a selected set of representative angiosperm genomes (three monocots and five dicots) and identified 10 main clusters, subdivided into 44 orthogroups (OGs). An expert curation for gene structures, orthogroup composition, and functional annotation was made based on a literature review. Then, using the HMM profiles as seeds, we expanded the classification to 46 plant species. Our results revealed the variable evolutionary dynamics between OGs in which some expanded, mostly through tandem duplications, while others were maintained as single copies. Among these, dicot-specific clusters and specific amplifications in monocots and wheat were characterized. This approach, by combining manual curation and automatic identification, was effective in characterizing a large gene family, allowing the establishment of a classification framework for gene function transfer and a better understanding of the evolutionary history of GELP.