Findings implicate GRF21 as a negative regulator of flowering time in maize, as evidenced by the delayed flowering phenotype associated with its overexpression, and highlights GRF21 as a promising target for maize breeding.
Abstract
Background
Flowering time represents a pivotal agronomic trait that determines regional adaptability and grain yield in maize (Zea mays). Members of the 14-3-3 protein family, also known as general regulatory factors (GRFs), function as central modulators of diverse developmental and physiological processes in plants. However, their specific roles in regulating flowering time in maize remain undefined.
Results
Here, we present a functional characterization of GRF21, a maize GRF family member, with particular emphasis on its role in floral transition. Through an integrative approach combining phylogenetic analysis, gene transformation, and genome-wide transcriptomic analysis, we show that constitutive overexpression of GRF21 delays flowering in maize, suggesting a potential role in flowering-time regulation. GRF21 localizes to both the nucleus and cytoplasm and accumulates predominantly in roots, stems, and reproductive tissues. Furthermore, transcriptomic analyses, supported by quantitative RT-PCR and dual-luciferase reporter assays, reveal that GRF21 represses the transcription of key flowering-promoting genes, including Zea mays CENTRORADIALIS 7 (ZCN7), ZCN8, and ZCN12, thereby suppressing floral transition.
Conclusions
Collectively, these findings implicate GRF21 as a negative regulator of flowering time in maize, as evidenced by the delayed flowering phenotype associated with its overexpression. This work expands the current molecular framework underlying floral initiation and highlights GRF21 as a promising target for maize breeding.
Evidence is provided suggesting that StFKF1 influences the timing of flowering and tuber initiation, as well as the expression patterns of key regulatory genes, under long-day conditions, thereby contributing to a theoretical foundation for understanding developmental transitions in this specific environmental context.
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A detailed understanding of the molecular mechanisms governing the flowering time of Amomum villosum Lour., a medicinal plant within the Zingiberaceae family, is currently lacking. In modern plants, the florigen activation complex (FAC), which includes PEBP, FD/bZIP, and GRF proteins, is known to regulate flowering. In this study, we identified 13 PEBP, 5 FD, and 19 GRF genes within the A. villosum genome and conducted phylogenetic, structural and promoter analysis. Notably, cross-species protein–protein interaction predictions and yeast two-hybrid assays uncovered an unexpected interaction pattern: an AREB3-like FD protein (AvFD5) and a GRF protein (AvGRF13) directly interact with specific PEBP members, whereas canonical FD-like proteins (AvFD1 and AvFD4) did not, which contrasts with the classical rice FAC model (Hd3a-14-3-3-OsFD1). These results imply that FAC assembly in A. villosum may involve alternative components or regulatory mechanisms, potentially indicating lineage-specific divergence within monocots. This research represents the first systematic characterization of FAC core gene families in A. villosum and Zingiberaceae, laying the groundwork for understanding flowering time regulation and facilitating future molecular breeding efforts in this economically significant plant.
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