Aug 2026· Proceedings of the National Academy of Sciences of the United States of America· Vol 123 35, pp.
e2605727123
· 0 citations· 43 references
Medicine
TL;DR
A florigen-induced regulatory mechanism that controls the reproductive-specific timing of AM initiation and provides a framework for understanding plasticity and diversification of shoot branching patterns is uncovered.
Abstract
Shoot branching patterns and their diversity arise from variable activities of axillary meristems (AMs). A common feature of flowering plants is delayed AM initiation and growth during the vegetative phase, followed by a sudden and rapid acceleration of apical AM initiation during the reproductive phase. The mechanisms underlying this pronounced developmental shift are poorly understood. During tomato floral transition, the primary shoot meristem (PSM) terminates in a flower after producing two spatially adjacent AMs: one that will generate a flower and the other a vegetative side shoot. In plants lacking the universal floral-promoting mobile protein florigen, these processes are uncoupled: The vegetative AM initiation is delayed, even though termination of the PSM into a flower is largely unaffected. To identify factors that promote AM initiation in response to flowering induction signals, we analyzed a high-temporal-density single-meristem transcriptome profile from wild-type and florigen-defective plants. Our analysis revealed two genes, PUCHI and LOB30, induced by florigen in incipient AMs. These genes promote rapid initiation of both the vegetative and reproductive AMs, with the latter facilitating formation of a multi-flower inflorescence. Counterintuitively, these genes act in parallel with a PSM maturation program that limits production of reproductive AMs. Together, our findings uncover a florigen-induced regulatory mechanism that controls the reproductive-specific timing of AM initiation and provides a framework for understanding plasticity and diversification of shoot branching patterns.
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.
Zefeng Zhai, Yongguang Liu, Haicai Li et al.· Molecular breeding· 0 citations
Background The capitulum of Asteraceae is a highly specialized inflorescence whose formation requires the coordinated regulation of multiple developmental processes, including floral organ identity and floral meristem determinacy. The LEAFY (LFY)–UNUSUAL FLORAL ORGANS (UFO) regulatory module is known to play an important role in flower development; however, naturally occurring mutations affecting this pathway have not been genetically characterized in gerbera (Gerbera hybrida). Results In this study, we characterized a novel gerbera mutant identified during a commercial crossing program and named it marimo based on its green, spherical capitulum. Morphological observations revealed the repeated formation of secondary and tertiary floret-like organs within primary floret-like organs. Scanning electron microscopy showed that the epidermal structure of the green organs in marimo was similar to that of wild-type involucral bracts. RNA sequencing identified numerous differentially expressed genes between marimo and the wild type, and network and Gene Ontology analyses highlighted gene groups associated with flower development, reproductive organ differentiation, and tissue structure formation. RNA-seq analysis showed increased expression of LFY and reduced expression of GGLO1, a PISTILLATA/GLOBOSA-like B-class MADS-box gene, in the marimo mutant. RT-qPCR analysis of a segregating population further confirmed reduced GGLO1 expression in marimo-type individuals. In addition, a single-nucleotide deletion was identified in the coding region of UFO. This deletion was predicted to cause a frameshift and a premature stop codon. In selfed progeny of No. 251, the UFO genotype was fully associated with capitulum phenotype, and only individuals homozygous for the mutant allele exhibited the marimo phenotype. Conclusions These results indicate that the naturally occurring frameshift mutation in UFO is the strongest candidate variant underlying the marimo phenotype. RNA-seq analysis showed increased LFY expression and markedly reduced GGLO1 expression in the marimo mutant. Reduced activity of the LFY–UFO regulatory module may therefore have altered the expression of GGLO1 and other floral organ development-related genes despite the continued expression of LFY. These changes may have affected both floral organ identity and floral meristem determinacy, resulting in the formation of green involucral bract-like organs and the repeated production of floret-like organs. The marimo mutant provides a useful genetic resource for investigating capitulum development in Asteraceae and may also serve as breeding material for introducing novel ornamental traits into gerbera.
Retention of vegetative meristems beyond the first year of flowering underpins perennial growth, yet the developmental mechanisms causing it remain unresolved. To address this knowledge gap, we quantified vegetative shoot branching and flowering architecture in eight annual–perennial species pairs within the grass subfamily Pooideae, tracking thousands of vegetative and reproductive branches within a phylogenetic framework to test whether perenniality is maintained through temporal delays in branch development or spatial segregation of vegetative and reproductive branches. Annuals, except Hordeum vulgare, produced branches at shorter intervals, flowered earlier, and showed more synchronized flowering than their perennial counterparts. Across life histories, flowering progressed from older to younger branches, with little evidence for consistent spatial segregation of vegetative and reproductive branches. In perennial species in the core group, younger branches during the first year of flowering had a lower probability of floral transition, reflecting delayed branch initiation and age‐dependent responsiveness to floral signals. Core perennial species branched faster than noncore perennials, indicating lineage‐specific differences in developmental pace. Our findings demonstrate that perennial Pooideae retain vegetative meristems through temporal delays in branch development rather than age‐independent spatial partitioning, providing a developmental mechanism for perennial persistence and a trait directly relevant to perennializing annual grain crops.
A. C. Hjertaas, H. Vinje, J. C. Preston et al.· New Phytologist· 0 citations
In the crop Brassica napus (oilseed rape), distinct growth types have been established that differ mainly in their vernalization requirement for flowering. The need for vernalization in Arabidopsis is controlled by the expression of the floral repressor FLOWERING LOCUS C (FLC), which also regulates cold-responsive flowering in B. napus. Notably, FLC homologs are also retained in spring oilseed rape despite its lack of vernalization requirement. To elucidate the functions of the nine BnFLC homologs in a spring type, we generated CRISPR/Cas9 knockout mutants of all homologs in the cultivar Westar. We show that the loss of BnFLC genes significantly accelerates flowering, demonstrating that BnFLC genes regulate flowering in spring types independently of vernalization. Transcriptomic analyses in leaves revealed distinct expression patterns among the BnFLC genes, with some remaining active during floral transition. Finally, no epigenetic regulation of the BnFLC homologs associated with flowering time was detected, while BnFLC.A03b carried persistent repressive marks and was constitutively silenced. Unexpectedly, additional flowering time regulators, including genes typically active in the shoot apical meristem, were expressed in leaves, with some showing altered expression and chromatin states in the mutant. These findings reveal that BnFLC genes are developmentally regulated and directly control flowering in spring oilseed rape, while also modulating the expression of other floral regulators in B. napus. CRISPR/Cas9 knockout of all nine BnFLC homologs reveals that these genes regulate flowering time developmentally in spring oilseed rape while influencing the expression and chromatin states of downstream flowering regulators.
Sarah Duveneck, Kea Ille, S. Melzer· Plant Molecular Biology· 0 citations
The initiation of floral organ primordia at the peripheral zone of the floral meristem (FM) is a fundamental process in flower development, yet its regulatory mechanisms in sunflower remain unclear. In this study, we characterized a sunflower space-mutagenized mutant, crazy broccoli 1 (cb1), in which FM-like structures fail to generate floral organs and maintain meristematic activity throughout development. This defect leads to floral development malformation, resulting in an indeterminate FM-like structure consisting of successive whorls of bracts and meristems. Through comparative transcriptomics and expression profile analysis of wild type and cb1 plants, we analyzed the expression dynamics of key gene families in regulating flower development, including APETALA2 (AP2), MADS-box, WUSCHEL (WUS), and LEAFY (LFY). We identified LFY, SHORT VEGETATIVE PHASE (SVP), AGAMOUS (AG), and WUS as central regulators of floral organogenesis. In cb1, elevated LFY and SVP-like transcription represses AG-like expression, which in turn relieves the repression on WUS-like. Sustained WUS-like activity prevents FM termination, leading to repeated formation of meristem-bract whorls. Conversely, in wild type plants, low LFY and SVP-like levels permit high AG-like expression, which suppresses WUS-like transcription and ensures timely FM termination and normal floral organogenesis. These findings provide clues for understanding the molecular mechanism underlying FM activity and floral organogenesis in sunflower.
Qian Wang, Deding Su, Jing Chen et al.· Plant Science· 0 citations
Perennial plants have evolved complex regulatory networks that allow them to perceive environmental changes and trigger adaptive growth responses. Many perennial herbs exhibit a rosette growth habit during winter, and then undergo extension growth/stem elongation growth and flowering in the following spring. However, the mechanisms underlying this seasonal transition are still not well understood. Here, using the perennial herb chrysanthemum (Chrysanthemum morifolium), we identified CmKN1, a class I KNOTTED (KN1)-like homeobox transcription factor, that mediates extension growth and flowering competence in response to prolonged chilling exposure. The rosette growth of chrysanthemum rhizomes in late autumn coincides with downregulation of CmKN1 expression. Overexpression of CmKN1 promotes premature rhizome extension growth and flowering, whereas the kn1 heterozygous mutant shows suppression of these processes. Furthermore, seasonal growth regulation involves the abscisic acid (ABA) signaling pathway. Shoot apices in the rosette state accumulate higher levels of ABA than those in the extension growth state. Notably, in response to ABA, CmKN1 expression is downregulated by CmABI5. Our results demonstrated that the CmABI5-CmKN1 module mediates extension growth and flowering competence in response to chilling, thereby facilitating the perennial growth habit of chrysanthemum.
Tianhua Jiang, Chang Luo, Chu-Qi Zhang et al.· New Phytologist· 0 citations