Linum usitatissimum FUSCA3-1 regulates plant architecture and seed storage reserve accumulation in Arabidopsis thaliana

Flax (Linum usitatissimum L.) as a self-pollinated annual diploid crop is grown worldwide primarily for its seed storage reserves of oil and storage proteins. The B3 domain transcription factor AtFUSCA3 (AtFUS3) has been identified as a master regulator of seed storage reserve accumulation in Arabidopsis thaliana. However, the function of LuFUS3 from L. usitatissimum has not yet been assessed. Here, we found that there were two LuFUS3 homologs, LuFUS3-1 and LuFUS3-2, in the L. usitatissimum genome. The subcellular localization and yeast transcriptional activation assays indicated that LuFUS3-1 functions as a transcription factor. Heterogeneous expression of LuFUS3-1 in the A. thaliana wild type background changed the plant architecture, including moderately dwarf stature, wrinkled leaves, increased branch number, altered floral morphology, and shorter and wider siliques, which was at least partially caused by the significantly decreased level of endogenous gibberellins. On the other hand, we demonstrated that LuFUS3-1 enhances the accumulation of seed storage reserves inclusive of oil and storage proteins in A. thaliana seeds. Consistently, LuFUS3-1 promotes the expression of many genes involved in the biosynthesis of seed oil and storage proteins during seed development. These findings provide new insights into the FUS3 function in plant architecture and seed storage reserve accumulation, and also represent a promising target for genetic modification of L. usitatissimum.

Automated summary

This study identified the function of LuFUS3-1 in flax, showing its role in regulating plant architecture and promoting the accumulation of seed storage reserves. It provides new insights into the understanding of FUS3 function and genetic modification of flax.