Biology subjects

Sakr, S.

Publications and source records attributed to Sakr, S..

7 recordsLinked to original sources

bioRxiv2026

Sugar metabolism drives shoot branching by repressing BRC1 through miR319-targeted TCP4 in Rosa.

The coupling between sugar availability and shoot branching is well established, yet the underlying molecular mechanisms remain largely unknown. Here, using genome-wide profiling, we characterized the sugar signalling pathways by identifying 10 miRNAs repressed by glycolysis, the tricarboxylic acid (TCA) cycle, and/or the oxidative pentose phosphate pathway (OPPP) in rose buds. Focusing on RhmiR319, a miRNA repressed under active sugar metabolism, we demonstrate that disruption of both glycolysis/the TCA cycle and the OPPP induces the RhmiR319 accumulation, leading to the concomitant repression of its targets, RhTCP4a and RhTCP4b. We additionally reveal that the miR319/TCP4 module regulates shoot branching in Arabidopsis, as miR319 overexpression impairs shoot branching, whereas TCP4 promotes it. Altered branching patterns in Rose and Arabidopsis were associated with the expression of the branching integrator BRC1. Finally, we provide molecular evidence supporting that RhTCP4a/b directly binds to the RhBRC1 promoter and represses its transcription. Together, these results establish the miR319-TCP4-BRC1 regulatory module as a key component in the regulation of shoot branching in response to sugar status. We propose that the miR319-TCP4-BRC1 module is conserved between annual and perennial species and may integrate multiple hormonal and metabolic signals to shape shoot branching in plants.

plant biology↗

bioRxiv2026

Branching Varies with Light Limitation Scenarios in relation with Changes in Carbon Source-Sink Dynamics.

Bud outgrowth is a major component of plant architectural plasticity and is influenced by light conditions. While the inhibitory effect of low light intensity on branching is well documented, the underlying regulators remain debated and, especially, the role of sugar availability has never been thoroughly evaluated. Here, we combined experiments with a computational approach quantifying carbon source-sink balance in single-axis rose plants to investigate how continuous and transient light limitation regulate bud outgrowth. Continuous low light reduced photosynthesis, leading to decreased sugar availability and inhibited bud outgrowth. In contrast, a transient period of low light followed by high light unexpectedly stimulated bud outgrowth, shortened the delay between outgrowth of successive buds, and produced an over-branched phenotype. This response resulted from a non-reversible reduction in the growth of apical organs appearing under low light, which lowered carbon demand and caused sugar over-accumulation after the return to high light. Manipulating carbon supply and demand through leaf masking, photosynthetic inhibition, and targeted sucrose feeding causally confirmed the central role of sugar availability in these contrasting responses. Beyond these findings, key requirements for models simulating branching plasticity were identified and this work provides a basis for predicting branching responses under fluctuating and complex light environments. HighlightBud outgrowth, a key component of plant plasticity, is regulated by light intensity through sugar availability. Continuous and transient low light have opposite effects by limiting sugar production and use, respectively.

plant biology↗

bioRxiv2023

Application of slow-controlled release fertilizer coordinates the carbon flow in carbon-nitrogen metabolism to effect rice quality

Slow-controlled release fertilizers are experiencing a popularity in rice cultivation due to their effectiveness in yield and quality with low environmental costs. However, the underlying mechanism by which these fertilizers regulate grain quality remains inadequately understood. This study investigated the effects of five fertilizer management practices on rice quality in a two-year field experiment: CK, conventional fertilization, and four applications of slow-controlled release fertilizer (UF, urea formaldehyde; SCU, sulfur-coated urea; PCU, polymer-coated urea; BBF, controlled-release bulk blending fertilizer). In 2020 and 2021, the yields of UF and SCU groups showed significant decreases when compared to conventional fertilization, accompanied by a decline in nutritional quality. Additionally, PCU group exhibited poorer cooking and eating qualities. However, BBF group achieved increases in both yield (10.8 t hm-2 and 11.0 t hm-2) and grain quality reaching the level of CK group. The sufficient nitrogen supply in both the PCU and BBF groups during the grain-filling stage led to a greater capacity for the accumulation of proteins and amino acids in the PCU group compared to starch accumulation. Intriguingly, BBF group showed better carbon-nitrogen metabolism than that of PCU group. The optimal nitrogen supply present in BBF group suitable boosted the synthesis of amino acids involved in the glycolysis/ tricarboxylic acid cycle, thereby effectively coordinating carbon-nitrogen metabolism. The application of the new slow-controlled release fertilizer, BBF, is advantageous in regulating the carbon flow in the carbon-nitrogen metabolism to enhance rice quality.

plant biology↗

bioRxiv2020

Sucrose represses the expression of the strigolactone signalling gene D3/RMS4/MAX2 to promote tillering

- Shoot branching, a major component of shoot architecture, is regulated by multiple signals. Previous studies have indicated that sucrose may promote branching through suppressing the inhibitory effect of the hormone strigolactone (SL). However, the molecular mechanisms underlying this effect are unknown. - Here we used molecular and genetic tools to identify the molecular targets underlying the antagonistic interaction between sucrose and SL. - We showed that sucrose antagonises the suppressive action of SL on tillering in rice and on the degradation of D53, a major target of SL signalling. Sucrose inhibits the expression of D3, the orthologue of the arabidopsis F-box protein MAX2 required for SL signalling. Over-expression of D3 prevents sucrose from inhibiting D53 degradation and enabled the SL inhibition of tillering under high sucrose. Sucrose also prevents SL-induced degradation of D14, the SL receptor involved in D53 degradation. Interestingly, D14 over-expression enhances D53 protein levels and sucrose-induced tillering. - Our results show that sucrose inhibits SL perception by targeting key components of SL signalling and, together with previous studies reporting the inhibition of SL synthesis by nitrate and phosphate, demonstrate the central role played by strigolactones in the regulation of plant architecture by nutrients.

plant biology↗

bioRxiv2020

HEXOKINASE1 interferes with cytokinin synthesis and strigolactone perception during sugar-induced shoot branching

- Plant architecture is controlled by several endogenous signals including hormones and sugars. However, only little is known about the nature and roles of the sugar signalling pathways in this process. Here we test whether the sugar pathway mediated by HEXOKINASE1 (HXK1) is involved in the control of shoot branching. - To test the involvement of HXK1 in the control of shoot architecture we modulated the HXK1 pathway using physiological and genetic approaches in diverse plants, rose, arabidopsis and pea and evaluated impacts of hormonal pathways. - We show that triggering a hexokinase-dependent pathway was able to promote bud outgrowth in pea and rose. In arabidopsis, both HXK1 deficiency and defoliation led to decreased shoot branching and conferred hypersensitivity to auxin. HXK1 expression was positively correlated with sugar availability. HXK1-deficient plants displayed decreased cytokinin levels and increased expression of MAX2 which is required for strigolactone signalling. The branching phenotype of HXK1-deficient plants could be partly restored by cytokinin treatment and strigolactone deficiency could override the negative impact of HXK1 deficiency on shoot branching. - Our observations demonstrate that a HXK1-dependent pathway contributes to the regulation of shoot branching and interact with hormones to modulate plant architecture.

plant biology↗

bioRxiv2019

Sugar availability suppresses the auxin-induced strigolactone pathway to promote bud outgrowth

O_LIApical dominance occurs when the growing shoot tip inhibits the outgrowth of axillary buds. Apically-derived auxin in the nodal stem indirectly inhibits bud outgrowth via cytokinins and strigolactones. Recently, sugar deprivation was found to contribute to this phenomenon.\nC_LIO_LIUsing rose and pea, we investigated whether sugar availability interacts with auxin in bud outgrowth control, and the role of cytokinins and strigolactones, in vitro and in planta.\nC_LIO_LIWe show that sucrose antagonizes auxins effect on bud outgrowth, in a dose-dependent and coupled manner. Sucrose also suppresses strigolactone-inhibition of outgrowth, and rms3 strigolactone-perception mutant is less affected by reducing sucrose supply; however, sucrose does not interfere with the regulation of cytokinin levels by auxin, and stimulates outgrowth even with optimal cytokinin supply. These observations were assembled into a computational model where sucrose represses bud response to strigolactones, largely independently of cytokinin levels. It quantitatively captures our observed dose-dependent sucrose-hormones effects on bud outgrowth, and allows us to express outgrowth response to various combinations of auxin and sucrose levels as a simple quantitative law.\nC_LIO_LIThis study places sugars in the bud outgrowth regulatory network, and paves the way for better understanding of branching plasticity in response to environmental and genotypic factors.\nC_LI

plant biology↗

bioRxiv2018

A high-quality sequence of Rosa chinensis to elucidate genome structure and ornamental traits

Rose is the worlds most important ornamental plant with economic, cultural and symbolic value. Roses are cultivated worldwide and sold as garden roses, cut flowers and potted plants. Rose has a complex genome with high heterozygosity and various ploidy levels. Our objectives were (i) to develop the first high-quality reference genome sequence for the genus Rosa by sequencing a doubled haploid, combining long and short read sequencing, and anchoring to a high-density genetic map and (ii) to study the genome structure and the genetic basis of major ornamental traits.\n\nWe produced a haploid rose line from R. chinensis Old Blush and generated the first rose genome sequence at the pseudo-molecule scale (512 Mbp with N50 of 3.4 Mb and L75 of 97). The sequence was validated using high-density diploid and tetraploid genetic maps. We delineated hallmark chromosomal features including the pericentromeric regions through annotation of TE families and positioned centromeric repeats using FISH. Genetic diversity was analysed by resequencing eight Rosa species. Combining genetic and genomic approaches, we identified potential genetic regulators of key ornamental traits, including prickle density and number of flower petals. A rose APETALA2 homologue is proposed to be the major regulator of petals number in rose. This reference sequence is an important resource for studying polyploidisation, meiosis and developmental processes as we demonstrated for flower and prickle development. This reference sequence will also accelerate breeding through the development of molecular markers linked to traits, the identification of the genes underlying them and the exploitation of synteny across Rosaceae.

genomics↗