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: Lun Zhao, Xue Jing, Li Chen, Yingjun Liu, Yanan Su, Tingting Liu, Changbin Gao, Bin Yi, Jing Wen, Chaozhi Ma, Jinxing Tu, Jitao Zou, Tingdong Fu, Jinxiong Shen
• Journal: Molecular plant (Mol Plant) Vol. 8 Issue 12 Pg. 1710-24 (Dec 07 2015) ISSN: 1752-9867 [Electronic] England
• PMID: 26362932 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Chemical References

• Arylsulfonates
• Herbicides
• Plant Proteins
• metsulfuron methyl
• Acetolactate Synthase

Topics

• Acetolactate Synthase (antagonists & inhibitors, genetics, metabolism)
• Arylsulfonates (toxicity)
• Autophagy (drug effects)
• Brassica napus (drug effects, enzymology, genetics, physiology)
• Down-Regulation (drug effects)
• Flowers (drug effects, enzymology, genetics, growth & development)
• Gene Expression Regulation, Developmental (drug effects)
• Gene Expression Regulation, Plant (drug effects)
• Herbicides (toxicity)
• Plant Infertility (drug effects)
• Plant Proteins (antagonists & inhibitors, genetics, metabolism)
• Pollen (cytology, drug effects, enzymology, genetics)