title: Tribenuron-Methyl Induces Male Sterility through Anther-Specific Inhibition of Acetolactate Synthase Leading to Autophagic Cell Death.
abstract: Tribenuron-methyl (TM) is a powerful sulfonylurea herbicide that inhibits branched-chain amino acid (BCAA) biosynthesis by targeting the catalytic subunit (CSR1) of acetolactate synthase (ALS). Selective induction of male sterility by foliar spraying of TM at low doses has been widely used for hybrid seed production in rapeseed (Brassica napus); however, the underlying mechanism remains unknown. Here, we report greater TM accumulation and subsequent stronger ALS inhibition and BCAA starvation in anthers than in leaves and stems after TM application. Constitutive or anther-specific expression of csr1-1D (a CSR1 mutant) eliminated anther-selective ALS inhibition and reversed the TM-induced male sterile phenotype in both rapeseed and Arabidopsis. The results of TM daub-stem experiments, combined with the observations of little TM accumulation in anthers and reversion of TM-induced male sterility by targeted expression of the TM metabolism gene Bel in either the mesophyll or phloem, suggested that foliar-sprayed TM was polar-transported to anthers mainly through the mesophyll and phloem. Microscopy and immunoblotting revealed that autophagy, a bulk degradation process induced during cell death, was elevated in TM-induced male sterile anthers and by anther-specific knockdown of ALS. Moreover, TM-induced pollen abortion was significantly inhibited by the autophagy inhibitor 3-MA. These data suggested that TM was polar-transported to anthers, resulting in BCAA starvation via anther-specific ALS inhibition and, ultimately, autophagic cell death in anthers.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Lun
authors.initials: L
authors.lastname: Zhao
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Jing
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Yingjun
authors.initials: Y
authors.lastname: Liu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Su
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Liu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Changbin
authors.initials: C
authors.lastname: Gao
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, 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, 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, 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, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Jinxing
authors.initials: J
authors.lastname: Tu
authors.affiliation: National Research Council Canada, Saskatoon, Saskatchewan S7N 0W9, Canada.
authors.forename: Jitao
authors.initials: J
authors.lastname: Zou
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, National Center of Rapeseed Improvement, 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, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: jxshen@mail.hzau.edu.cn.
authors.forename: Jinxiong
authors.initials: J
authors.lastname: Shen
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D001190:Arylsulfonates / Q000633:toxicity*; D001343:Autophagy / Q000187:drug effects; D029688:Brassica napus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D015536:Down-Regulation / Q000187:drug effects; D035264:Flowers / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006540:Herbicides / Q000633:toxicity*; D051479:Plant Infertility / Q000187:drug effects*; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011058:Pollen / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000235:genetics
chemical_list: D001190:Arylsulfonates; D006540:Herbicides; D010940:Plant Proteins; C050296:metsulfuron methyl; D000095:Acetolactate Synthase
keywords: Brassica napus; acetolactate synthase; amino acid starvation; autophagy; chemical hybridizing agent; male sterility