Background:
Acetolactate synthase (ALS)-inhibiting
herbicides amidosulfuron (Hoestar) is an efficient gametocide that can induce
male sterility in rapeseed (Brassica napus L.). We conducted an integrated study of cytological, transcriptomic, and physiological analysis to decipher the gametocidal effect of
amidosulfuron. Results: In the first several days after exposure to
amidosulfuron at a gametocidal dose of ca. 1 μg per plant, the plants showed the earliest symptoms including short retard of raceme elongation, slight
chlorosis on leaf, and decrease of photosynthesis rate. Chloroplasts in leaf and anther epidermis, and tapetal plastids were deformed. Both tapetal cell and uni-nucleate microspore showed autophagic vacuoles and degenerated quickly. The
amidosulfuron treatment caused reduction of photosynthetic rate and the contents of leaf
chlorophyll, soluble
sugar and
pyruvate, as well as content alteration of several free
amino acids in the treated plants. A comparison of transcriptomic profiling data of the young flower buds of the treated plants with the control identified 142 up-regulated and 201 down-regulated differential expression transcripts with functional annotations. Down-regulation of several interesting genes encoding PAIR1, SDS, PPD2, HFM1, CSTF77, A6, ALA6, UGE1, FLA20, A9, bHLH91, and putative cell wall
protein LOC106368794, and up-regulation of
autophagy-related protein ATG8A indicated functional abnormalities about cell cycle, cell wall formation, chloroplast structure, and tissue autophagy.
Ethylene-responsive
transcription factor RAP2-11-like was up-regulated in the flower buds and
ethylene release rate was also elevated. The transcriptional regulation in the
amidosulfuron-treated plants was in line with the cytological and physiological changes. Conclusions: The results suggested that metabolic decrease related to photosynthesis and energy supply are associated with
male sterility induced by
amidosulfuron. The results provide insights into the molecular mechanisms of gametocide-induced
male sterility and expand the knowledge on the transcriptomic complexity of the plants exposure to sulfonylurea
herbicide.