FUSCA3-induced AINTEGUMENTA-like 6 manages seed dormancy and lipid metabolism

The transcription factor AINTEGUMENTA-like6 manages seed dormancy and lipid metabolism, acting downstream of the master regulator FUSCA3. FUSCA 3 (FUS3), a seed master regulator, plays critical role in seed dormancy and oil accumulation. However, its downstream regulation mechanisms remain poorly understood. Here, we explored the roles of AINTEGUMENTA-like 6 (AIL6), a seed transcription factor, in these processes. The activation of AIL6 by FUS3 was demonstrated by dual-LUC assay. Seeds of ail6 mutants showed alterations in fatty acid compositions, and both AtAIL6 (AIL6 from Arabidopsis thaliana) and BnaAIL6 (AIL6 from Brassica napus) rescued the phenotype. Over-expression (OE) of AIL6s reversed changes in seed fatty acid composition. Notably, OE lines showed low seed germination rates down to 12% compared to 100% of wild-type Col-0. Transcriptome analysis of the mutant and an OE line indicated widespread expression changes of genes involved in lipid metabolism and phytohormone pathways. In OE mature seeds, GA(4) content decreased more than 15-fold, while abscisic acid and indole-3-acetic acid (IAA) contents clearly increased. Exogenous GA(3) treatments did not effectively rescue the low germination rate. Nicking seed coats increased germination rates from 25% to nearly 80% while the wild-type rdr6-11 is 100% and 98% respectively, and elongation of storage time also improved seed germination. Furthermore, dormancy imposed by AIL6 was fully released in the della quintuple mutant. Together, our results indicate AIL6 acts as a manager downstream of FUS3 in seed dormancy and lipid metabolism.

Automated summary

The transcription factor AINTEGUMENTA-like6 functions as a downstream regulator of the master regulator FUSCA3 in seed dormancy and lipid metabolism. AIL6 is activated by FUS3 and has a role in modulating fatty acid compositions in seeds. Over-expression of AIL6 leads to low seed germination rates and alterations in lipid metabolism, which can be released by the della quintuple mutant.