MdBRC1 and MdFT2 Interaction Fine-Tunes Bud Break Regulation in Apple
Authors: Gioppato, H. A., Estevan, J., Al Bolbol, M., Soriano, A., Garighan, J., Jeong, K., Georget, C., Soto, D. G., El Khoury, S., Falavigna, V. d. S., George, S., Perales, M., Andres, F.
The study identifies the transcription factor MdBRC1 as a key inhibitor of bud growth during the ecodormancy phase in apple (Malus domestica), directly regulating dormancy‑associated genes and interacting with the flowering promoter MdFT2 to modulate bud break. Comparative transcriptomic analysis and gain‑of‑function experiments in poplar demonstrate that MdFT2 physically binds MdBRC1, attenuating its repressive activity and acting as a molecular switch for the transition to active growth.
The study engineers Type‑B response regulators to alter their transcriptional activity and cytokinin sensitivity, enabling precise modulation of cytokinin‑dependent traits. Using tissue‑specific promoters, the synthetic transcription factors were deployed in Arabidopsis thaliana to reliably increase or decrease lateral root numbers, demonstrating a modular platform for controlling developmental phenotypes.
The study introduced full-length SOC1 genes from maize and soybean, and a partial SOC1 gene from blueberry, into tomato plants under constitutive promoters. While VcSOC1K and ZmSOC1 accelerated flowering, all three transgenes increased fruit number per plant mainly by promoting branching, and transcriptomic profiling revealed alterations in flowering, growth, and stress‑response pathways.
Arabidopsis lines with modified ascorbate concentrations reveal a link between ascorbate and auxin biosynthesis
Authors: Fenech, M., Zulian, V., Moya-Cuevas, J., Arnaud, D., Morilla, I., Smirnoff, N., Botella, M. A., Stepanova, A. N., Alonso, J. M., Martin-Pizarro, C., Amorim-Silva, V.
The study used Arabidopsis thaliana mutants with low (vtc2, vtc4) and high (vtc2/OE-VTC2) ascorbate levels to examine how ascorbate concentration affects gene expression and cellular homeostasis. Transcriptomic analysis revealed that altered ascorbate levels modulate defense and stress pathways, and that TAA1/TAR2‑mediated auxin biosynthesis is required for coping with elevated ascorbate in a light‑dependent manner.
The study characterizes the tomato class B heat shock factor SlHSFB3a, revealing its age‑dependent expression in roots and its role in enhancing lateral root density by modulating auxin homeostasis. Overexpression of SlHSFB3a increases lateral root emergence, while CRISPR‑mediated knockouts produce the opposite phenotype, indicating that SlHSFB3a regulates auxin signaling through repression of auxin repressors and activation of the ARF7/LOB20 pathway.
A forward genetic screen in light-grown Arabidopsis seedlings identified the Evening Complex component ELF3 as a key inhibitor of phototropic hypocotyl bending under high red:far-red and blue light, acting upstream of PIF4/PIF5. ELF3 and its partner LUX also mediate circadian regulation of phototropism, and the orthologous ELF3 in Brachypodium distachyon influences phototropism in the opposite direction.
The study investigates the altered timing of the core circadian oscillator gene ELF3 in wheat compared to Arabidopsis, revealing that dawn-specific expression in wheat arises from repression by TOC1. An optimized computational model integrating experimental expression data and promoter architecture predicts that wheat’s circadian oscillator remains robust despite this shift, indicating flexibility in plant circadian network design.
The study tests whether the circadian clock component ELF3 shapes developmental trait heterogeneity, proposing that faster‑developing populations are more heterogeneous early but less so at maturity, whereas slower growers show the opposite pattern. Experiments with Arabidopsis elf3 and barley Hvelf3 mutants confirmed these predictions, showing ELF3 influences hypocotyl and bolting variability via maturation rate, and that smaller barley plants exhibit increased osmotic stress resilience, suggesting ELF3‑driven heterogeneity serves as a bet‑hedging strategy.