Death of female flower microsporocytes progresses independently of meiosis-like process and can be accelerated by specific transcripts in Asparagus officinalis

Abstract

Asparagus officinalis (garden asparagus) is a dioecious perennial crop, and the dioecy (i.e., sex) of A. officinalis can affect its productivity. In A. officinalis , flower anthers in female plants fail to accumulate callose around microsporocytes, fail to complete meiosis, and degenerate due to cell death. Although 13 genes have been implicated in the anther development of male and female flowers, it is unclear how these genes regulate the cell death in female flower anthers. The aim of this study was to narrow down factors involved in this process. TUNEL staining and Feulgen staining of female flower microsporocytes suggest that female microsporocytes enter a previously undetected meiosis-like process, and that the cell death occurs independently of this meiosis-like process, excluding the possibility that the cell death is caused by the cessation of meiosis. RNA sequencing with individual floral organs (tepals, pistils and stamens) revealed that several genes possibly regulating the cell death, such as metacaspase genes and a Bax inhibitor-1 gene, are differentially regulated between female and male flower anthers, and that genes involved in callose accumulation are up-regulated only in male flower anthers. These genes are likely involved in regulating the cell death in female flower anthers in A. officinalis .

Developmental differences between hermaphrodite and female-like flowers in a non-model horticultural plant <i>Dianthus hybrida</i>

“…4). Therefore, putative defect in meio-sis during microsporogenesis might not be a factor that causes the degeneration and shrinking of microspores in female-like flowers later, just as it was suggested to be in the case of Asparagus officinalis (Ide et al 2019). Another possible factor was ethylene, which is revealed to be produced in pistil and causes anther arrest in the flower of Cucumis species (Boualem et al 2008, Manzano et al 2016.…”

Data of whole genome sequencing of five garden asparagus (Asparagus officinalis) individuals with the MinION nanopore sequencer

“…The reads derived from the MinION sequencing were mapped to the existing A. officinalis genome sequence, which derived from a supermale individual (NCBI RefSeq accession: GCF_001876935.1) [3], with the MegaBLAST aligner in the BLAST + suite [5] with default parameters. The putative A. officinalis transcript sequences that were derived from RNA sequencing [1,2] and that were not mapped to the above-mentioned genome sequence [4] (‘orphan genes’) were mapped to the MinION-derived reads with MegaBLAST with default parameters. Flanking sequences and genomic positions of five randomly chosen orphan genes were estimated with those MegaBLAST results.…”

“…Raw data obtained from the MinION sequencing were deposited as FASTQ format in the NCBI SRA database (accession numbers: SRR9643835-SRR9643839, Table 1 “Data accessibility”). In a previous study, ∼2% of the A. officinalis gene fragments, which had been obtained from de novo assembly of RNA sequencing-derived reads [1,2], were not mapped to the existing A. officinalis genome sequence [4]. With the help of the MinION-derived data, flanking sequences of five of such gene fragments were cloned, and their genomic positions were estimated (Table 2).…”

“…The resulting FAST5 files were converted to FASTQ files with the Albacore basecaller (version 2.1.3, ONT). The resulting read sequences were compared with the existing A. officinalis transcript sequences and the supermale genome sequence [[1], [2], [3], [4]] with the MegaBLAST aligner [5]. On the basis of this result, flanking sequences of five gene fragments whose genomic positions were unknown were determined by genomic PCR followed by Sanger sequencing.Data source locationHokkaido UniversitySapporo-shi, Hokkaido, JapanNorth latitude 43°07′ and east longitude 141°34′Data accessibilityRepository name: NCBI (National Center for Biotechnology Information) SRA (Sequence Read Archive) and Nucleotide databasesData identification number: SRR9643835-SRR9643839 (SRA); MN311180-MN311184 (Nucleotide)Direct URL to data:https://www.ncbi.nlm.nih.gov/sra (SRA)https://www.ncbi.nlm.nih.gov/nuccore (Nucleotide)…”