Abstract

Selective abortion of initiated organs helps plants maintain growth under energy limitation, but its regulatory basis remains unclear. In sacred lotus (Nelumbo nucifera), shading strongly promotes flower bud abortion. Here, we identify NnFLZ2, a shade-responsive FCS-like zinc finger protein, as a candidate regulator associated with this process. Population genomic analysis revealed strong divergence at the NnFLZ2 locus between flower lotus and rhizome lotus, mainly in the upstream regulatory region. Consistently, NnFLZ2 expression was elevated in low-flowering germplasms and aborting flower buds. Functional analyses in lotus showed that NnFLZ2 promotes shade-associated flower bud abortion while supporting vegetative growth under low light. In Arabidopsis, NnFLZ2 overexpression enhanced tolerance to carbon starvation and promoted reproductive termination under darkness, suggesting partial functional similarity in energy-stress responses. Mechanistically, NnFLZ2 interacts with NnSnRK1 in the nucleus and represses NnSnRK1 promoter activity. Genetic and autophagy-related assays further suggest that NnFLZ2 and NnSnRK1 act in a closely associated pathway and promote autophagy-related processes linked to flower bud abortion. These findings identify NnFLZ2 as a shade-responsive regulator associated with lotus flower bud fate.