Biology subjects

Noll, G. A.

Publications and source records attributed to Noll, G. A..

3 recordsLinked to original sources

bioRxiv2025

Temperature-regulated FLOWERING LOCUS T homologs make distinct contributions to the floral transition in vernalization-dependent and vernalization-independent Taraxacum koksaghyz plants

Flowering that requires a period of cold (vernalization) is a key trait in many crops, but the underlying regulatory pathways are often poorly understood. Taraxacum koksaghyz is a rubber-producing dandelion of the family Asteraceae, which also includes other economically important crops such as chicory and lettuce. Most T. koksaghyz plants require cold exposure to induce flowering, but plants that have lost the dependence on vernalization are more suitable for domestication and breeding. To provide insight into the molecular basis of mandatory vernalization in T. koskaghyz, we identified three FLOWERING LOCUS T (FT) homologs (TkFT1-3) that are differentially expressed under varying environmental conditions. TkFT1 and TkFT2 are expressed under long-day conditions at ambient temperatures whereas only TkFT1 is weakly expressed under short-day conditions. Exposure to cold was shown to repress TkFT1 but induce TkFT3. Overexpression experiments revealed that TkFT1-3 bypass the vernalization requirement in T. koksaghyz and its close relative T. officinale, and promote early flowering in vernalization-independent T. brevicorniculatum. We also identified two FRUITFULL homologs (TkFUL1 and TkFUL2) as downstream targets, which were upregulated in TkFT overexpression lines. Our findings suggest that TkFT1 promotes vernalization-independent flowering, whereas TkFT3 expression during the cold period is needed to promote vernalization-dependent flowering. This study explicates the regulatory network controlling flowering time in T. koksaghyz, contributing to a broader understanding of flowering in the family Asteraceae and providing knowledge that can be used in the future to facilitate domestication and breeding. Key messageIn Taraxacum koksaghyz, FT homologs function as floral inducers that upregulate FRUITFULL homologs, with TkFT1 linked to vernalization-independent flowering and TkFT3 associated with the acquisition of flowering competence during vernalization.

developmental biology↗

bioRxiv2022

Gene complementation analysis suggests that dodder plants (Cuscuta spp.) do not depend on the host FT protein for flowering

Dodder (Cuscuta spp.) is a genus of parasitic plants that form physiological bridges (haustoria) with their hosts to facilitate the transfer of water and nutrients. The parasites also repurpose nucleic acids and proteins translocating through the haustoria, potentially including the host florigen protein (FT), which is postulated to trigger floral transition in the parasite. Here, we identified the endogenous FT-FD flowering module in Cuscuta campestris. We detected the expression of two parasite-encoded C. campestris (Cc)FT genes in haustoria, whereas a newly found CcFD-like gene was expressed ubiquitously. C. campestris flowered while growing on mutant tobacco plants lacking the floral activators NtFT4 and NtFT5, indicating that host FT proteins are not required to initiate the parasites floral transition. We also showed that CcFT1 (identical to CaFT from Cuscuta australis) and CcFT2 can rescue a non-flowering Ntft4-Ntft5- double knockout tobacco phenotype. Together, our results show that Cuscuta spp. produce a potent endogenous florigen as well as other proteins likely to be involved in floral transition. FT gene expression profiles in the haustoria suggest that Cuscuta spp. transition to flowering at least partly in response to host signals (e.g., sugars) that can activate the parasites FT-FD module. Although C. campestris and C. australis appear not to depend on the host FT protein for floral transition, the nature of the mobile host signals that influence floral development in these parasites remain unclear. Significance StatementParasitic higher plants are known for their sophisticated adaptations that facilitate the transfer of water and nutrients from their hosts. They can also synchronize their transition from vegetative to reproductive development to match the host plant. Despite this high degree of synchronization, dodder plants maintain a potent endogenous floral activator module, which enables the parasite to switch to reproductive development autonomously. Synchronization must therefore involve other stimuli from the host plant, which are currently unknown. Understanding the environmental cues that trigger flowering, and the corresponding network of genetic and physiological regulators and integrators, may lead to new strategies that reduce the reproductive fitness of parasitic plants to protect crops and ensure food security. Data ServersThis article is available as preprint (ID: BIORXIV/2022/520981) at https://www.biorxiv.org under the CC BY-NC 4.0 license. Reusable data files have been deposited at https://datadryad.org, accessible during peer-review under: https://datadryad.org/stash/share/DK8Olh2VqFwbGNL0GtkGt24dD0GhWhJn82oLBC1XK70

plant biology↗

bioRxiv2022

Unraveling the mystery behind the short-day-specific flowering of tobacco cultivar Maryland Mammoth

Flowering in day-neutral tobacco (Nicotiana tabacum) plants requires the photoperiod-dependent expression of members of the FLOWERING LOCUS T (FT)-like clade of phosphatidylethanolamine-binding proteins. FT-like floral activators and inhibitors compete for interaction with FD proteins to shift from vegetative to reproductive growth. In the short-day (SD) cultivar Maryland Mammoth (MM), vegetative growth persists under long-day (LD) conditions, generating unusually tall plants. We found that the major floral inducer under long-days (NtFT5) was expressed in MM and that NtFT5 overexpression induced flowering in MM plants under LD conditions. However, sequence analysis revealed a 2-bp deletion near the 3 end of NtFT5 in MM plants resulting in a frame shift which leads to an altered amino acid sequence and a premature stop codon. We found that the truncated NtFT5MM protein was still able to interact with tobacco FD proteins. However, constitutive overexpression under LD conditions in SD-specific flowering tobacco plants showed that NtFT5MM is a weaker floral inducer than NtFT5. Our data suggest that the truncation does not impair the stability of the NtFT5MM protein but may affect its binding affinity for NtFD1, probably resulting in the weaker expression of target genes. Our results therefore provide a potential explanation for the MM gigantism phenotype first observed more than 100 years ago. HighlightThe previously unexplained gigantism of Maryland Mammoth tobacco is caused by a truncated major floral activator protein that results in weaker activation and the inability to flower under long-day conditions.

plant biology↗