Functional characterization of a novel Brassica LEAFY homolog from Indian mustard: Expression pattern and gain-of-function studies

•Expression domains of novel homolog (BjuLFY) is fine-mapped to stage 1-4 of primary floral buds in B. juncea suggesting its role in floral transition ; expression in root samples implied neo-functionalization.•Similar LFY expression in early stages of bud development in 15 cultivars of 6 crop Brassica species implied functional conservation.•Ectopic expression of BjuLFY in A. thaliana and B. juncea caused floral meristem defects and precocious flowering confirmed its role as floral regulator in B. juncea.•GC-MS analysis of mature seed from Brassica transgenics showed an altered fatty-acid profile suggestive of seed maturation occurring at lower temperatures due to early flowering.

LEAFY plays a central role in regulation of flowering time and floral meristem identity in plants. Unfortunately, LFY function remains uncharacterized in agronomicaly important Brassicas. Herein, we illustrate fine-mapping of expression domains of LFY in 15 cultivars of 6 Brassica species and describe gain-of-function phenotypes in Arabidopsis and Brassica. We depict early flowering and altered fatty-acid composition in transgenic seed. The cDNA encoding BjuLFY (417aa) shared only 85% identity with reported homolog of B.juncea implying distinctness. Quantitative RT-PCR based coarse expression mapping of BjuLFY in tissue samples representing 3 time points at specific days after sowing (DAS), pre-flowering (30 DAS), flowering (75 DAS) and post-flowering (110 DAS), depicted an intense pulse of BjuLFY expression restricted to primary floral buds (75 DAS) which subsided in secondary floral buds (110 DAS); expression in root samples was also recorded implying neo-functionalization. Fine-mapping of expression during flowering confirmed tightly regulated LFY expression during early stages of bud development in 15 cultivars of 6 Brassica species implying functional conservation. Ectopic expression of BjuLFY in A. thaliana and B. juncea caused floral meristem defects and precocious flowering. B. juncea transgenics (T1) over-expressing BjuLFY flowered 20 days earlier produced normal flowers. GC-MS analysis of mature seed from Brassica transgenics showed an altered fatty-acid profile suggestive of seed maturation occurring at lower temperatures vis-à-vis control. Our findings implicate BjuLFY as a regulator of flowering in B. juncea and suggest its application in developing climate resilient crops.