title: Ectopic Expression of BnaC.CP20.1 Results in Premature Tapetal Programmed Cell Death in Arabidopsis.
abstract: Tapetal programmed cell death (PCD) is essential in pollen grain development, and cysteine proteases are ubiquitous enzymes participating in plant PCD. Although the major papain-like cysteine proteases (PLCPs) have been investigated, the exact functions of many PLCPs are still poorly understood in PCD. Here, we identified a PLCP gene, BnaC.CP20.1, which was closely related to XP_013596648.1 from Brassica oleracea. Quantitative real-time PCR analysis revealed that BnaC.CP20.1 expression was down-regulated in male-sterile lines in oilseed rape, suggesting a connection between this gene and male sterility. BnaC.CP20.1 is especially active in the tapetum and microspores in Brassica napus from the uninucleate stage until formation of mature pollen grains during anther development. On expression of BnaC.CP20.1 prior to the tetrad stage, BnA9::BnaC.CP20.1 transgenic lines in Arabidopsis thaliana showed a male-sterile phenotype with shortened siliques containing fewer or no seeds by self-crossing. Scanning electron microscopy indicated that the reticulate exine was defective in aborted microspores. Callose degradation was delayed and microspores were not released from the tetrad in a timely fashion. Additionally, the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay indicated that BnaC.CP20.1 ectopic expression led to premature tapetal PCD. Transmission electron microscopy analyses further demonstrated that the pollen abortion was due to the absence of tectum connections to the bacula in the transgenic anthers. These findings suggest that timely expression of BnaC.CP20.1 is necessary for tapetal degeneration and pollen wall formation.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Song
authors.affiliation: Wheat Research Institute, Henan Academy of Agricultural Sciences, Zhengzhou 450002, China.
authors.forename: Zhengfu
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Tang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Shengqian
authors.initials: S
authors.lastname: Xia
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Maomao
authors.initials: M
authors.lastname: Qin
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Bao
authors.initials: B
authors.lastname: Li
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wen
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yi
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jinxiong
authors.initials: J
authors.lastname: Shen
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Chaozhi
authors.initials: C
authors.lastname: Ma
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Tingdong
authors.initials: T
authors.lastname: Fu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement in Wuhan, Huazhong Agricultural University, Wuhan 430070, China tujx@mail.hzau.edu.cn.
authors.forename: Jinxing
authors.initials: J
authors.lastname: Tu
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics*; D029688:Brassica napus / Q000166:cytology / Q000235:genetics*; D016923:Cell Death / Q000235:genetics; D000066630:Ectopic Gene Expression; D035264:Flowers / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D010802:Phylogeny; D051479:Plant Infertility / Q000235:genetics; D030821:Plants, Genetically Modified / Q000166:cytology; D011058:Pollen / Q000166:cytology / Q000235:genetics / Q000254:growth & development; D011401:Promoter Regions, Genetic
keywords: BnaC.CP20.1; Brassica napus; Cysteine proteases; Male sterility; Pollen exine; Tapetal PCD