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SUMMARY: The successful interaction between pollen and stigma is a critical process for plant sexual reproduction, involving a series of intricate molecular and physiological events. After self‐compatible pollination, a significant reduction in reactive oxygen species (ROS) production has been observed in stigmas, which is essential for pollen grain rehydration and subsequent pollen tube growth. Several scavenging enzymes tightly regulate ROS homeostasis. However, the potential role of these ROS‐scavenging enzymes in the pollen‐stigma interaction in Brassica napus remains unclear. Here, we showed that the activity of ascorbate peroxidase (APX), an enzyme that plays a crucial role in the detoxification of hydrogen peroxide (H2O2), was modulated depending on the compatibility of pollination in B. napus. We then identified stigma‐expressed APX1s and generated pentuple mutants of APX1s using CRISPR/Cas9 technology. After compatible pollination, the BnaAPX1 pentuple mutants accumulated higher levels of H2O2 in the stigma, while the overexpression of BnaA09.APX1 resulted in lower levels of H2O2. Furthermore, the knockout of BnaAPX1 delayed the compatible response‐mediated pollen rehydration and germination, which was consistent with the effects of a specific APX inhibitor, ρ‐Aminophenol, on compatible pollination. In contrast, the overexpression of BnaA09.APX1 accelerated pollen rehydration and germination after both compatible and incompatible pollinations. However, delaying and promoting pollen rehydration and germination did not affect the seed set after compatible and incompatible pollination in APX1 pentuple mutants and overexpression lines, respectively. Our results demonstrate the fundamental role of BnaAPX1 in pollen rehydration and germination by regulating ROS homeostasis during the pollen‐stigma interaction in B. napus. Significance Statement: Our research found that self‐incompatibility in Brassica napus requires the accumulation of reactive oxygen species (ROS) levels in the stigma. We identified the importance of BnaAPX1 in regulating ROS homeostasis, which is critical for pollen rehydration and germination in B. napus. [ABSTRACT FROM AUTHOR]

SUMMARY: Canola (Brassica napus) is an important oil crop worldwide. The seed‐setting rate (SS) is a critical factor in determining its yield, and the development of pistils affects pollination and seed sets. However, research on seed‐setting defects has been limited owing to difficulties in the identification of phenotypes, mutations, and complex genetic mechanisms. In this study, we found a stigma defect (sd) mutant in B. napus, which had no nectary. The SS of sd mutants in the field was approximately 93.4% lower than that of the wild type. Scanning and transmission electron microscopy imaging of sd mutants showed a low density of stigma papillary cells and stigma papillary cell vacuoles that disappeared 16 h after flowering. Genetic analysis of segregated populations showed that two recessive nuclear genes are responsible for the mutant phenotype of sd. Based on re‐sequencing and map‐based cloning, we reduced the candidate sites on ChrA07 (BnaSSA07) and ChrC06 (BnaSSC06) to 30 and 67 kb, including six and eight predicted genes, respectively. Gene analyses showed that a pair of CRABS CLAW (CRC) homeologous genes at BnaSSA07 and BnaSSC06 were associated with the development of carpel and nectary. BnaSSA07.CRC and BnaSSC06.CRC candidate genes were found to be expressed in flower organs only, with significant differences in their expression in the pistils of the near‐isogenic lines. DNA sequencing showed transposon insertions in the upstream region and intron of the candidate gene BnaSSA07.crc. We also found that BnaSSC06.crc exists widely in the natural population and we give possible reasons for its widespread existence. Significance Statement: The BnaCRCs of domesticated preference are located at A07 and C06 within 30‐ and 67‐kb regions, respectively, as determined by re‐sequencing and map‐based cloning. They were positively correlated with the Brassica napus seed‐setting rate. [ABSTRACT FROM AUTHOR]

Alternative splicing ( AS) is a key post-transcriptional regulatory mechanism, yet little information is known about its roles in fruit crops. Here, AS was globally analyzed in the wild strawberry Fragaria vesca genome with RNA-seq data derived from different stages of fruit development. The AS landscape was characterized and compared between the single-molecule, real-time ( SMRT) and Illumina RNA-seq platform. While SMRT has a lower sequencing depth, it identifies more genes undergoing AS (57.67% of detected multiexon genes) when it is compared with Illumina (33.48%), illustrating the efficacy of SMRT in AS identification. We investigated different modes of AS in the context of fruit development; the percentage of intron retention ( IR) is markedly reduced whereas that of alternative acceptor sites ( AA) is significantly increased post-fertilization when compared with pre-fertilization. When all the identified transcripts were combined, a total of 66.43% detected multiexon genes in strawberry undergo AS, some of which lead to a gain or loss of conserved domains in the gene products. The work demonstrates that SMRT sequencing is highly powerful in AS discovery and provides a rich data resource for later functional studies of different isoforms. Further, shifting AS modes may contribute to rapid changes of gene expression during fruit set. [ABSTRACT FROM AUTHOR]