Photocontrol of bud burst involves gibberellin biosynthesis in Rosa sp

Inhibition of flowering by gibberellins in the woody plant Jatropha curcas is restored by overexpression of JcFT

Jatropha curcas (J. curcas) is a perennial oil-seed plant with vigorous vegetative growth but relatively poor reproductive growth and low seed yield. Gibberellins (GAs) promotes flowering in most annual plants but inhibits flowering in many woody plants, including J. curcas. However, the underlying mechanisms of GA inhibits flowering in perennial woody plants remain unclear. Here, we found that overexpression of the GA biosynthesis gene JcGA20ox1 inhibits flowering in J. curcas and in J. curcas × J. integerrima hybrids. Consistent with this finding, overexpression of the GA catabolic gene JcGA2ox6 promotes flowering in J. curcas. qRTPCR revealed that inhibits floral transition by overexpressing JcGA20ox1 resulted from a decrease in the expression of JcFT and other flowering-related genes, which was restored by overexpressing JcFT in J. curcas. Overexpression of JcGA20ox1 or JcGA2ox6 reduced seed yield, but overexpression of JcFT significantly increased seed yield. Furthermore, hybridization experiments showed that the reduction in seed yield caused by overexpression of JcGA20ox1 or JcGA2ox6 was partially restored by the overexpression of JcFT. In addition, JcGA20ox1, JcGA2ox6 and JcFT were also found to be involved in the regulation of seed oil content and endosperm development. In conclusion, our study revealed that the inhibitory effect of GA on flowering is mediated through JcFT and demonstrated the effects of JcGA20ox1, JcGA2ox6 and JcFT on agronomic traits in J. curcas. This study also indicates the potential value of GA metabolism genes and JcFT in the breeding of new varieties of woody oil-seed plants.

Unveiling the effect of gibberellin-induced iron oxide nanoparticles on bud dormancy release in sweet cherry (Prunus avium L.)

Hydrogen cyanide has been extensively used worldwide for bud dormancy break in fruit trees, consequently enhancing fruit production via expedited cultivation, especially in areas with controlled environments or warmer regions. A novel and safety nanotechnology was developed since the hazard of hydrogen cyanide for the operators and environments, there is an urgent need for the development of novel and safety approaches to replace it to break bud dormancy for fruit trees. In current study, we have systematically explored the potential of iron oxide nanoparticles, specifically α-Fe2O3, to modulate bud dormancy in sweet cherry (Prunus avium). The synthesized iron oxide nanoparticles underwent meticulous characterization and assessment using various techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and ultraviolet-visible infrared (UV-Vis) spectroscopy. Remarkably, when applied at a concentration of 10 mg L-1 alongside gibberellin (GA4+7), these iron oxide nanoparticles exhibited a substantial 57% enhancement in bud dormancy release compared to control groups, all achieved within a remarkably short time span of 4 days. Our RNA-seq analyses further unveiled that 2757 genes within the sweet cherry buds were significantly up-regulated when treated with 10 mg L-1 α-Fe2O3 nanoparticles in combination with GA, while 4748 genes related to dormancy regulation were downregulated in comparison to the control. Moreover, we discovered an array of 58 transcription factor families among the crucial differentially expressed genes (DEGs). Through hormonal quantification, we established that the increased bud burst was accompanied by a reduced concentration of abscisic acid (ABA) at 761.3 ng/g fresh weight in the iron oxide treatment group, coupled with higher levels of gibberellins (GAs) in comparison to the control. Comprehensive transcriptomic and metabolomic analyses unveiled significant alterations in hormone contents and gene expression during the bud dormancy-breaking process when α-Fe2O3 nanoparticles were combined with GA. In conclusion, our findings provide valuable insights into the intricate molecular mechanisms underlying the impact of iron oxide nanoparticles on achieving uniform bud dormancy break in sweet cherry trees.

How do brassinosteroids fit in bud outgrowth models?

A network of plant hormonal signals coordinates plant branching. Brassinosteroids are important in this network, acting as repressors of the strigolactone pathway and TEOSINTE BRANCHED1 .

Transcriptome analysis during axillary bud growth in chrysanthemum (chrysanthemum×morifolium)

The chrysanthemum DgLsL gene, homologous with tomato Ls, is one of the earliest expressed genes controlling axillary meristem initiation. In this study, the wild-type chrysanthemum (CW) and DgLsL-overexpressed line 15 (C15) were used to investigate the regulatory mechanism of axillary bud development in chrysanthemum. Transcriptome sequencing was carried out to detect the differentially expressed genes of the axillary buds 0 h, 24 h and 48 h after decapitation. The phenotypic results showed that the number of axillary buds of C15 was significantly higher than CW. A total of 9,224 DEGs were identified in C15-0 vs. CW-0, 10,622 DEGs in C15-24 vs. CW-24, and 8,929 DEGs in C15-48 vs. CW-48.GO and KEGG pathway enrichment analyses showed that the genes of the flavonoid, phenylpropanoids and plant hormone pathways appeared to be differentially expressed, indicating their important roles in axillary bud germination. DgLsL reduces GA content in axillary buds by promoting GA2ox expression.These results confirmed previous studies on axillary bud germination and growth, and revealed the important roles of genes involved in plant hormone biosynthesis and signal transduction, aiding in the study of the gene patterns involved in axillary bud germination and growth.

Light on perenniality: Para-dormancy is based on ABA-GA antagonism and endo-dormancy on the shutdown of GA biosynthesis

Perennial para- and endo-dormancy are seasonally separate phenomena. Whereas para-dormancy is the suppression of axillary buds (AXBs) by a growing shoot, endo-dormancy is the short-day elicited arrest of terminal and AXBs. In hybrid aspen (Populus tremula x P. tremuloides) compromising the apex releases para-dormancy, whereas endo-dormancy requires chilling. ABA and GA are implicated in both phenomena. To untangle their roles, we blocked ABA biosynthesis with fluridone (FD), which significantly reduced ABA levels, downregulated GA-deactivation genes, upregulated the major GA3ox-biosynthetic genes, and initiated branching. Comprehensive GA-metabolite analyses suggested that FD treatment shifted GA production to the non-13-hydroxylation pathway, enhancing GA₄ function. Applied ABA counteracted FD effects on GA metabolism and downregulated several GA_3/4 -inducible α- and γ-clade 1,3-β-glucanases that hydrolyze callose at plasmodesmata (PD), thereby enhancing PD-callose accumulation. Remarkably, ABA-deficient plants repressed GA₄ biosynthesis and established endo-dormancy like controls but showed increased stress sensitivity. Repression of GA₄ biosynthesis involved short-day induced DNA methylation events within the GA3ox2 promoter. In conclusion, the results cast new light on the roles of ABA and GA in dormancy cycling. In para-dormancy, PD-callose turnover is antagonized by ABA, whereas in short-day conditions, lack of GA₄ biosynthesis promotes callose deposition that is structurally persistent throughout endo-dormancy.

Spectral light quality regulates the morphogenesis, architecture, and flowering in pepper (Capsicum annuum L.)

Transparent plastic films with poor light transmittance seriously affect the mass composition of visible light in many greenhouses, which leads to the reduction of photosynthesis in vegetable crops. Understanding the regulatory mechanisms of monochromatic light in the vegetative and reproductive growth of vegetable crops is of great importance for the application of light-emitting diodes (LEDs) in the greenhouse. In this study, three monochromatic light treatments (red-, green- and blue-light) were simulated by using LEDs to explore light quality-dependent regulation from the stage of seedling to flowering in pepper (Capsicum annuum L.). The results showed that light quality-dependent regulation guides the growth and morphogenesis in pepper plants. Red- and blue-light played opposite roles in determining the plant height, stomatal density, axillary bud growth, photosynthetic characteristics, flowering time and hormone metabolism, while green light treatment resulted in taller plants and fewer branches, which was similar to the red-light treatment. The weighted correlation network analysis (WGCNA) based on mRNA-seq results revealed that the two modules named "MEred" and "MEmidnightblue" were positively correlated with red- and blue-light treatment, respectively, exhibiting high correlations with the traits such as plant hormone content, branching and flowering. Moreover, our results suggest that the light response factor ELONGATED HYPOCOTYL 5 (HY5) is essential for blue light-induced plant growth and development by regulating photosynthesis in pepper plants. Hence, this study uncovers crucial molecular mechanisms of how light quality determines the morphogenesis, architecture, and flowering in pepper plants, thus providing a basic concept of manipulating light quality to regulate pepper plant growth and flowering under greenhouse conditions.

The Roles of Gibberellins in Regulating Leaf Development

Plant growth and development are correlated with many aspects, including phytohormones, which have specific functions. However, the mechanism underlying the process has not been well elucidated. Gibberellins (GAs) play fundamental roles in almost every aspect of plant growth and development, including cell elongation, leaf expansion, leaf senescence, seed germination, and leafy head formation. The central genes involved in GA biosynthesis include GA20 oxidase genes (GA20oxs), GA3oxs, and GA2oxs, which correlate with bioactive GAs. The GA content and GA biosynthesis genes are affected by light, carbon availability, stresses, phytohormone crosstalk, and transcription factors (TFs) as well. However, GA is the main hormone associated with BR, ABA, SA, JA, cytokinin, and auxin, regulating a wide range of growth and developmental processes. DELLA proteins act as plant growth suppressors by inhibiting the elongation and proliferation of cells. GAs induce DELLA repressor protein degradation during the GA biosynthesis process to control several critical developmental processes by interacting with F-box, PIFS, ROS, SCLl3, and other proteins. Bioactive GA levels are inversely related to DELLA proteins, and a lack of DELLA function consequently activates GA responses. In this review, we summarized the diverse roles of GAs in plant development stages, with a focus on GA biosynthesis and signal transduction, to develop new insight and an understanding of the mechanisms underlying plant development.

The Strigolactone Pathway Is a Target for Modifying Crop Shoot Architecture and Yield

Due to their sessile nature, plants have developed the ability to adapt their architecture in response to their environment. Branching is an integral component of plant architecture, where hormonal signals tightly regulate bud outgrowth. Strigolactones (SLs), being a novel class of phytohormone, are known to play a key role in branching decisions, where they act as a negative regulator of bud outgrowth. They can achieve this by modulating polar auxin transport to interrupt auxin canalisation, and independently of auxin by acting directly within buds by promoting the key branching inhibitor TEOSINTE BRANCHED1. Buds will grow out in optimal conditions; however, when conditions are sub-optimal, SL levels increase to restrict branching. This can be a problem in agricultural applications, as reductions in branching can have deleterious effects on crop yield. Variations in promoter elements of key SL-related genes, such as IDEAL PLANT ARCHITECTURE1, have been identified to promote a phenotype with enhanced yield performance. In this review we highlight how this knowledge can be applied using new technologies to develop new genetic variants for improving crop shoot architecture and yield.

Exogenous Phytohormones and Fertilizers Enhance Jatropha curcas L. Growth through the Regulation of Physiological, Morphological, and Biochemical Parameters

Jatropha curcas L. is a perennial plant, that emerged as a biodiesel crop attracting the great interest of researchers. However, it is considered a semi-wild plant and needed to apply crop-improving practices to enhance its full yield potential. This study was conducted to improve the growth and development of the J. curcas plant by exogenous application of Gibberellic acid (GA), indole acetic acid (IAA), and fertilizer (nitrogen, phosphorus, potassium (NPK)). The experiment was conducted in pots in triplicate and 100 ppm and 250 ppm of GA and IAA were applied separately while NPK was applied in two levels (30 and 60 g/pot). The results revealed a significant difference in growth parameters with the application of hormones and fertilizer. The highest shoot length (47%), root length (63%), root fresh weight (72%), and root dry weight (172%) were shown by plants treated with GA 250 ppm. While plants treated with NPK 60 g showed the highest increases in shoot fresh weight and shoot dry weight compared to control plants. The highest increase in leaves number (274%) and branches number (266%) were shown by the plants treated with GA 100 ppm and GA 250 ppm, respectively, while GA 250 ppm and IAA 250 ppm highly increased stem diameter (123%) and stem diameter was also shown by GA 250 ppm-treated plants. NPK 60 g highly increased proximate composition (protein content, carbohydrate, fat, moisture content, and ash content) compare with hormones and control plants. Our results concluded the optimized concentration of IAA, GA, and NPK significantly increases J. curcas growth vigor.

Identification of Key Genes Related to Dormancy Control in Prunus Species by Meta-Analysis of RNAseq Data

Bud dormancy is a genotype-dependent mechanism observed in Prunus species in which bud growth is inhibited, and the accumulation of a specific amount of chilling (endodormancy) and heat (ecodormancy) is necessary to resume growth and reach flowering. We analyzed publicly available transcriptome data from fifteen cultivars of four Prunus species (almond, apricot, peach, and sweet cherry) sampled at endo- and ecodormancy points to identify conserved genes and pathways associated with dormancy control in the genus. A total of 13,018 genes were differentially expressed during dormancy transitions, of which 139 and 223 were of interest because their expression profiles correlated with endo- and ecodormancy, respectively, in at least one cultivar of each species. The endodormancy-related genes comprised transcripts mainly overexpressed during chilling accumulation and were associated with abiotic stresses, cell wall modifications, and hormone regulation. The ecodormancy-related genes, upregulated after chilling fulfillment, were primarily involved in the genetic control of carbohydrate regulation, hormone biosynthesis, and pollen development. Additionally, the integrated co-expression network of differentially expressed genes in the four species showed clusters of co-expressed genes correlated to dormancy stages and genes of breeding interest overlapping with quantitative trait loci for bloom time and chilling and heat requirements.

Roles of auxin in the inhibition of shoot branching in 'Dugan' fir

Shoot branching substantially impacts vegetative and reproductive growth as well as wood characteristics in perennial woody species by shaping the shoot system architecture. Although plant hormones have been shown to play a fundamental role in shoot branching in annual species, their corresponding actions in perennial woody plants are largely unknown, in part due to the lack of branching mutants. Here, we demonstrated the role of plant hormones in bud dormancy transition toward activation and outgrowth in woody plants by comparing the physiological and molecular changes in the apical shoot stems of 'Yangkou' 020 fir and 'Dugan' fir, two Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) clones with normal and completely abolished branching phenotypes, respectively. Our studies showed that the defect in bud outgrowth was the cause of failed shoot branching in 'Dugan' fir whereas apically derived signals acted as triggers of this ectopic bud activity. Further studies indicated that auxin played a key role in inhibiting bud outgrowth in 'Dugan' fir. During bud dormancy release, the differential auxin resistant 1/Like AUX1 (AUX1/LAX) and PIN-formed (PIN) activity resulted in an ectopic auxin/indole-3-acetic acid (IAA) accumulation in the apical shoot stem of 'Dugan' fir, which could inhibit the cell cycle in the axillary meristem by decreasing cytokinin (CK) biosynthesis but increasing abscisic acid (ABA) production and response through the signaling pathway. In contrast, during bud activation and outgrowth, the striking increase in auxin biosynthesis and PIN activity in the shoot tip of 'Dugan' fir may trigger the correlative inhibition of axillary buds by modulating the polar auxin transport stream (PATS) and connective auxin transport (CAT) in shoots, and by influencing the biosynthesis of secondary messengers, including CK, gibberellin (GA) and ABA, thereby inducing the paradormancy of axillary buds in 'Dugan' fir by apical dominance under favorable conditions. The findings of this study provide important insights into the roles of plant hormones in bud outgrowth control in perennial woody plants.

Purification and Characterization of Gum-Derived Polysaccharides of Moringa oleifera and Azadirachta indica and Their Applications as Plant Stimulants and Bio-Pesticidal Agents

Plant gums are bio-organic substances that are derived from the barks of trees. They are biodegradable and non-adverse complex polysaccharides that have been gaining usage in recent years due to a number of advantages they contribute to various applications. In this study, gum was collected from Moringa oleifera and Azadirachta indica trees, then dried and powdered. Characterizations of gum polysaccharides were performed using TLC, GC-MS, NMR, etc., and sugar molecules such as glucose and xylose were found to be present. Effects of the gums on Abelmoschus esculentus growth were observed through root growth, shoot growth, and biomass content. The exposure of the seeds to the plant gums led to bio stimulation in the growth of the plants. Poor quality soil was exposed to the gum polysaccharide, where the polysaccharide was found to improve soil quality, which was observed through soil analysis and SEM analysis of soil porosity and structure. Furthermore, the plant gums were also found to have bio-pesticidal activity against mealybugs, which showed certain interstitial damage evident through histopathological analysis.

Whole genome re-sequencing and transcriptome reveal an alteration in hormone signal transduction in a more-branching mutant of apple

Branch number is an important trait in grafted apple breeding and cultivation. To provide new information on molecular mechanisms of apple branching, whole reduced-representation genomes and transcriptome of a wild-type (WT) apple (Malus spectabilis) and its more-branching (MB) mutant at the branching stage were examined in this study. Comparison of WT and MB genomes against the Malus domestica reference genome identified 14,908,939 single nucleotide polymorphisms (SNPs) and 173,315 insertions and deletions (InDels) in WT and 1,483,221 SNPs and 1,725,977 InDels in MB. Analysis of the genetic variation between MB and WT revealed 1,048,575 SNPs and 37,327 InDels. Among them, 24,303 SNPs and 891 InDels mapped to coding regions of 5,072 and 596 genes, respectively. GO and KEGG functional annotation of 3,846 and 944 genes, respectively, identified 32 variant genes related to plant hormone signal transduction that were involved in auxin, cytokinin, gibberellin, abscisic acid, ethylene, and brassinosteroid pathways. The transcriptome pathways of plant hormone signal transduction and zeatin biosynthesis were also significantly enriched during MB branching. Furthermore, transcriptome data suggested the regulatory roles of auxin signaling, increase of cytokinin and genes of cytokinin synthesis and signaling, and the suppressed abscisic acid signaling. Our findings suggest that branching development in apple is regulated by plant hormone signal transduction.

Exogenous 6-Benzyladenine Improved the Ear Differentiation of Waterlogged Summer Maize by Regulating the Metabolism of Hormone and Sugar

Waterlogging (W-B) is a major abiotic stress during the growth cycle of maize production in Huang-huai-hai plain of China, threatening food security. A wide range of studies suggests that the application of 6-benzyladenine (6-BA) can mitigate the W-B effects on crops. However, the mechanisms underlying this process remain unclear. In this study, the application of 6-BA that effectively increased the yield of summer maize was confirmed to be related to the hormone and sugar metabolism. At the florets differentiation stage, application of 6-BA increased the content of trans-zeatin (TZ, + 59.3%) and salicylic acid (SA, + 285.5%) of ears to induce the activity of invertase, thus establishing sink strength. During the phase of sexual organ formation, the TZ content of ear leaves, spike nodes, and ears was increased by 24.2, 64.2, and 46.1%, respectively, in W-B treatment, compared with that of W. Accordingly, the sugar metabolism of summer maize was also improved. Therefore, the structure of the spike node was improved, promoting the translocation of carbon assimilations toward the ears and the development of ears and filaments. Thus the number of fertilized florets, grain number, and yield were increased by the application of 6-BA.

Correlation analysis of the transcriptome and metabolome reveals the role of the flavonoid biosynthesis pathway in regulating axillary buds in upland cotton (Gossypium hirsutum L.)

Flavonoids are involved in axillary bud development in upland cotton. The phenylpropanoid and flavonoid biosynthesis pathways regulate axillary bud growth by promoting the transport of auxin in upland cotton. In cotton production, simplified cultivation and mechanical harvesting are emerging trends that depend on whether the cotton plant type meets production requirements. The axillary bud is an important index of cotton plant-type traits, and the molecular mechanism of axillary bud development in upland cotton has not yet been completely studied. Here, a combined investigation of transcriptome and metabolome analyses in G. hirsutum CCRI 117 at the fourth week (stage 1), fifth week (stage 2) and sixth week (stage 3) after seedling emergence was performed. The metabolome results showed that the total lipid, amino acid and organic acid contents in the first stalk node decreased during axillary bud development. The abundance of 71 metabolites was altered between stage 2 and stage 1, and 32 metabolites exhibited significantly altered abundance between stage 3 and stage 2. According to the correlation analysis of metabolome and transcriptome profiles, we found that phenylpropanoid and flavonoid biosynthesis pathways exhibit high enrichment degrees of both differential metabolites and differential genes in three stages. Based on the verification of hormone, soluble sugar and flavonoid detection, we propose a model for flavonoid-mediated regulation of axillary bud development in upland cotton, revealing that the decrease in secondary metabolites of phenylpropanoid and flavonoid biosynthesis is an essential factor to promote the transport of auxin and subsequently promote the growth of axillary buds. Our findings provide novel insights into the regulation of phenylpropanoid and flavonoid biosynthesis in axillary bud development and could prove useful for cultivating machine-harvested cotton varieties with low axillary buds.

Ascorbate-glutathione pathways mediated by cytokinin regulate H2O2 levels in light-controlled rose bud burst

Rosebush (Rosa "Radrazz") plants are an excellent model to study light control of bud outgrowth since bud outgrowth only arises in the presence of light and never occurs in darkness. Recently, we demonstrated high levels of hydrogen peroxide (H2O2) present in the quiescent axillary buds strongly repress the outgrowth process. In light, the outgrowing process occurred after H2O2 scavenging through the promotion of Ascorbic acid-Glutathione (AsA-GSH)-dependent pathways and the continuous decrease in H2O2 production. Here we showed Respiratory Burst Oxidase Homologs expression decreased in buds during the outgrowth process in light. In continuous darkness, the same decrease was observed although H2O2 remained at high levels in axillary buds, as a consequence of the strong inhibition of AsA-GSH cycle and GSH synthesis preventing the outgrowth process. Cytokinin (CK) application can evoke bud outgrowth in light as well as in continuous darkness. Furthermore, CKs are the initial targets of light in the photocontrol process. We showed CK application to cultured buds in darkness decreases bud H2O2 to a level that is similar to that observed in light. Furthermore, this treatment restores GSH levels and engages bud burst. We treated plants with buthionine sulfoximine, an inhibitor of GSH synthesis, to solve the sequence of events involving H2O2/GSH metabolisms in the photocontrol process. This treatment prevented bud burst, even in the presence of CK, suggesting the sequence of actions starts with the positive CK effect on GSH that in turn stimulates H2O2 scavenging, resulting in initiation of bud outgrowth.

Photocontrol of Axillary Bud Outgrowth by MicroRNAs: Current State-of-the-Art and Novel Perspectives Gained From the Rosebush Model

Shoot branching is highly dependent on environmental factors. While many species show some light dependence for branching, the rosebush shows a strict requirement for light to allow branching, making this species an excellent model to further understand how light impinges on branching. Here, in the first part, we provide a review of the current understanding of how light may modulate the complex regulatory network of endogenous factors like hormones (SL, IAA, CK, GA, and ABA), nutrients (sugar and nitrogen), and ROS to control branching. We review the regulatory contribution of microRNAs (miRNAs) to branching in different species, highlighting the action of such evolutionarily conserved factors. We underline some possible pathways by which light may modulate miRNA-dependent regulation of branching. In the second part, we exploit the strict light dependence of rosebush for branching to identify putative miRNAs that could contribute to the photocontrol of branching. For this, we first performed a profiling of the miRNAs expressed in early light-induced rosebush buds and next tested whether they were predicted to target recognized regulators of branching. Thus, we identified seven miRNAs (miR156, miR159, miR164, miR166, miR399, miR477, and miR8175) that could target nine genes (CKX1/6, EXPA3, MAX4, CYCD3;1, SUSY, 6PFK, APX1, and RBOHB1). Because these genes are affecting branching through different hormonal or metabolic pathways and because expression of some of these genes is photoregulated, our bioinformatic analysis suggests that miRNAs may trigger a rearrangement of the regulatory network to modulate branching in response to light environment.

Transcriptome analyses provide insights into the homeostatic regulation of axillary buds in upland cotton (G. hirsutum L.)

BACKGROUND

The axillary bud is an important index of cotton plant-type traits, and the molecular mechanism of axillary bud development in upland cotton has not yet been reported. We obtained a mutant (designated mZ571) with a high-budding phenotype in axillary bud development from the low-budding phenotype variety G. hirsutum Z571 (CCRI 9A02), which provided ideal materials for the study of complex regulatory networks of axillary bud development. In this study, RNA sequencing was carried out to detect gene expression levels during three stages of axillary buds in Z571 (LB, low budding) and mZ571 mutant (HB, high budding).

RESULTS

A total of 7162 DEGs were identified in the three groups (HB-E vs. LB-E, HB-G1 vs. LB-G1, HB-G2 vs. LB-G2), including 4014 downregulated and 3184 upregulated DEGs. Additionally, 221 DEGs were commonly identified in all three groups, accounting for approximately 3.09% of the total DEGs. These DEGs were identified, annotated and classified. A significant number of DEGs were related to hormone metabolism, hormone signal transduction, and starch and sucrose metabolism. In addition, 45, 22 and 9 DEGs involved in hormone metabolic pathways and 67, 22 and 19 DEGs involved in hormone signal transduction pathwayspathway were identified in HB-E vs. LB-E, HB-G1 vs. LB-G1, and HB-G2 vs. LB-G2, respectively, suggesting that endogenous hormones are the primary factors influencing cotton axillary bud growth. Hormone and soluble sugar content measurements revealed that mZ571 exhibited higher concentrations of zeatin, gibberellins and soluble sugar in all three stages, which confirmed that these hormone metabolism-, hormone signal transduction- and starch metabolism-related genes showed interaction effects contributing to the divergence of axillary bud growth between mZ571 and Z571.

CONCLUSIONS

Our results confirmed the importance of endogenous hormones and sugars in the development of axillary buds, and we found that mZ571 plants, with a high-budding phenotype of axillary buds, exhibited higher endogenous hormone and sugar concentrations. Overall, we present a model for the emergence and development of cotton axillary buds that provides insights into the complexity and dynamic nature of the regulatory network during axillary bud emergence and development.

Changes in carbohydrate metabolism and endogenous hormone regulation during bulblet initiation and development in Lycoris radiata

BACKGROUND

Lycoris species have great ornamental and medicinal values; however, their low regeneration efficiency seriously restricts their commercial production. Understanding the mechanism of bulblet propagation in this genus, which has remained underexplored to date, could provide a theoretical basis for improving the reproductive efficiency. Therefore, we studied the bulblet initiation and developmental processes in Lycoris radiata.

RESULTS

We found that bulblets are formed on the junctions of the innermost layers of scales and the basal plate, and initially present as an axillary bud and gradually develop into a bulblet. We also determined the changes in carbohydrate and endogenous hormone contents during bulblet initiation and development, as well as the expression patterns of genes involved in carbohydrate metabolism and hormone biosynthesis and signaling through transcriptome analysis. Soluble sugars derived from starch degradation in the outer scales are transported to and promote bulblet initiation and development through starch synthesis in the inner scales. This process is mediated by several genes involved in carbohydrate metabolism, especially genes encoding ADP glucose pyrophosphorylase, a crucial starch synthesis enzyme. As for hormones, endogenous IAA, GA, and ABA content showed an increase and decrease during bulblet initiation and development, respectively, which were consistent with the expression patterns of genes involved in IAA, GA, and ABA synthesis and signal transduction. In addition, a decrease in ZR content may be down- and up-regulated by CK biosynthesis and degradation related genes, respectively, with increasing auxin content. Furthermore, expression levels of genes related to BR, JA, and SA biosynthesis were increased, while that of ethylene biosynthesis genes was decreased, which was also consistent with the expression patterns of their signal transduction genes.

CONCLUSIONS

The present study provides insights into the effect of carbohydrate metabolism and endogenous hormone regulation on control of L. radiata bulblet initiation and development. Based on the results, we propose several suggestions to improve L. radiata propagation efficiency in production, which will provide directions for future research.

A Conceptual Framework for Winter Dormancy in Deciduous Trees

The perennial life strategy of temperate trees relies on establishing a dormant stage during winter to survive unfavorable conditions. To overcome this dormant stage, trees require cool (i.e., chilling) temperatures as an environmental cue. Numerous approaches have tried to decipher the physiology of dormancy, but these efforts have usually remained relatively narrowly focused on particular regulatory or metabolic processes, recently integrated and linked by transcriptomic studies. This work aimed to synthesize existing knowledge on dormancy into a general conceptual framework to enhance dormancy comprehension. The proposed conceptual framework covers four physiological processes involved in dormancy progression: (i) transport at both whole-plant and cellular level, (ii) phytohormone dynamics, (iii) genetic and epigenetic regulation, and (iv) dynamics of nonstructural carbohydrates. We merged the regulatory levels into a seasonal framework integrating the environmental signals (i.e., temperature and photoperiod) that trigger each dormancy phase.

Dual Role of Gibberellin in Perennial Shoot Branching: Inhibition and Activation

Shoot branching from axillary buds (AXBs) is regulated by a network of inhibitory and promotive forces, which includes hormones. In perennials, the dwarfed stature of the embryonic shoot inside AXBs is indicative of gibberellin (GA) deficiency, suggesting that AXB activation and outgrowth require GA. Nonetheless, the role of GA in branching has remained obscure. We here carried out comprehensive GA transcript and metabolite analyses in hybrid aspen, a perennial branching model. The results indicate that GA has an inhibitory as well as promotive role in branching. The latter is executed in two phases. While the expression level of GA2ox is high in quiescent AXBs, decapitation rapidly downregulated it, implying increased GA signaling. In the second phase, GA3ox2-mediated de novo GA-biosynthesis is initiated between 12 and 24 h, prior to AXB elongation. Metabolite analyzes showed that GA_1/4 levels were typically high in proliferating apices and low in the developmentally inactive, quiescent AXBs, whereas the reverse was true for GA_3/6. To investigate if AXBs are differently affected by GA₃, GA₄, and GR24, an analog of the branch-inhibitor hormone strigolactone, they were fed into AXBs of single-node cuttings. GA₃ and GA₄ had similar effects on GA and SL pathway genes, but crucially GA₃ induced AXB abscission whereas GA₄ promoted outgrowth. Both GA₃ and GA₄ strongly upregulated GA2ox genes, which deactivate GA_1/4 but not GA_3/6. Thus, the observed production of GA_3/6 in quiescent AXBs targets GA_1/4 for GA2ox-mediated deactivation. AXB quiescence can therefore be maintained by GA_3/6, in combination with strigolactone. Our discovery of the distinct tasks of GA₃ and GA₄ in AXB activation might explain why the role of GA in branching has been difficult to decipher. Together, the results support a novel paradigm in which GA_3/6 maintains high levels of GA2ox expression and low levels of GA₄ in quiescent AXBs, whereas activation and outgrowth require increased GA_1/4 signaling through the rapid reduction of GA deactivation and subsequent GA biosynthesis.

Light Regulation of Axillary Bud Outgrowth Along Plant Axes: An Overview of the Roles of Sugars and Hormones

Apical dominance, the process by which the growing apical zone of the shoot inhibits bud outgrowth, involves an intricate network of several signals in the shoot. Auxin originating from plant apical region inhibits bud outgrowth indirectly. This inhibition is in particular mediated by cytokinins and strigolactones, which move from the stem to the bud and that respectively stimulate and repress bud outgrowth. The action of this hormonal network is itself modulated by sugar levels as competition for sugars, caused by the growing apical sugar sink, may deprive buds from sugars and prevents bud outgrowth partly by their signaling role. In this review, we analyze recent findings on the interaction between light, in terms of quantity and quality, and apical dominance regulation. Depending on growth conditions, light may trigger different pathways of the apical dominance regulatory network. Studies pinpoint to the key role of shoot-located cytokinin synthesis for light intensity and abscisic acid synthesis in the bud for R:FR in the regulation of bud outgrowth by light. Our analysis provides three major research lines to get a more comprehensive understanding of light effects on bud outgrowth. This would undoubtedly benefit from the use of computer modeling associated with experimental observations to deal with a regulatory system that involves several interacting signals, feedbacks, and quantitative effects.

Role of Cytokinin, Strigolactone, and Auxin Export on Outgrowth of Axillary Buds in Apple

Shoot branching is regulated by phytohormones, including cytokinin (CK), strigolactone (SL), and auxin in axillary buds. The correlative importance of these phytohormones in the outgrowth of apple axillary buds remains unclear. In this study, the outgrowth dynamics of axillary buds of a more-branching mutant (MB) and its wild-type (WT) of Malus spectabilis were assessed using exogenous chemical treatments, transcriptome analysis, paraffin section, and reverse transcription-quantitative PCR analysis (RT-qPCR). High contents of CK and abscisic acid coincided in MB axillary buds. Exogenous CK promoted axillary bud outgrowth in the WT but not in MB, whereas exogenous gibberellic had no significant effect on bud outgrowth in the WT. Functional analysis of transcriptome data and RT-qPCR analysis of gene transcripts revealed that MB branching were associated with CK signaling, auxin transport, and SL signaling. Transcription of the SL-related genes MsMAX1, MsD14, and MsMAX2 in the axillary buds of MB was generally upregulated during bud outgrowth, whereas MsBRC1/2 were generally downregulated both in WT and MB. Exogenous SL inhibited outgrowth of axillary buds in the WT and the apple varieties T337, M26, and Nagafu 2, whereas axillary buds of the MB were insensitive to SL treatment. Treatment with N-1-naphthylphalamic acid (NPA; an auxin transport inhibitor) inhibited bud outgrowth in plants of the WT and MB. The transcript abundance of MsPIN1 was generally decreased in response to NPA and SL treatments, and increased in CK and decapitation treatments, whereas no consistent pattern was observed for MsD14 and MsMAX2. Collectively, the present results suggest that in apple auxin transport from the axillary bud to the stem may be essential for the outgrowth of axillary buds, and at least, is involved in the process of bud outgrowth.

BRANCHED1: A Key Hub of Shoot Branching

Shoot branching is a key process for plant growth and fitness. Newly produced axes result from axillary bud outgrowth, which is at least partly mediated through the regulation of BRANCHED1 gene expression (BRC1/TB1/FC1). BRC1 encodes a pivotal bud-outgrowth-inhibiting transcription factor belonging to the TCP family. As the regulation of BRC1 expression is a hub for many shoot-branching-related mechanisms, it is influenced by endogenous (phytohormones and nutrients) and exogenous (light) inputs, which involve so-far only partly identified molecular networks. This review highlights the central role of BRC1 in shoot branching and its responsiveness to different stimuli, and emphasizes the different knowledge gaps that should be addressed in the near future.

Hormonal Orchestration of Bud Dormancy Cycle in Deciduous Woody Perennials

Woody perennials enter seasonal dormancy to avoid unfavorable environmental conditions. Plant hormones are the critical mediators regulating this complex process, which is subject to the influence of many internal and external factors. Over the last two decades, our knowledge of hormone-mediated dormancy has increased considerably, primarily due to advancements in molecular biology, omics, and bioinformatics. These advancements have enabled the elucidation of several aspects of hormonal regulation associated with bud dormancy in various deciduous tree species. Plant hormones interact with each other extensively in a context-dependent manner. The dormancy-associated MADS (DAM) transcription factors appear to enable hormones and other internal signals associated with the transition between different phases of bud dormancy. These proteins likely hold a great potential in deciphering the underlying mechanisms of dormancy initiation, maintenance, and release. In this review, a recent understanding of the roles of plant hormones, their cross talks, and their potential interactions with DAM proteins during dormancy is discussed.

The Sugar-Signaling Hub: Overview of Regulators and Interaction with the Hormonal and Metabolic Network

Plant growth and development has to be continuously adjusted to the available resources. Their optimization requires the integration of signals conveying the plant metabolic status, its hormonal balance, and its developmental stage. Many investigations have recently been conducted to provide insights into sugar signaling and its interplay with hormones and nitrogen in the fine-tuning of plant growth, development, and survival. The present review emphasizes the diversity of sugar signaling integrators, the main molecular and biochemical mechanisms related to the sugar-signaling dependent regulations, and to the regulatory hubs acting in the interplay of the sugar-hormone and sugar-nitrogen networks. It also contributes to compiling evidence likely to fill a few knowledge gaps, and raises new questions for the future.

The Sugar-Signaling Hub: Overview of Regulators and Interaction with the Hormonal and Metabolic Network

Plant growth and development has to be continuously adjusted to the available resources. Their optimization requires the integration of signals conveying the plant metabolic status, its hormonal balance, and its developmental stage. Many investigations have recently been conducted to provide insights into sugar signaling and its interplay with hormones and nitrogen in the fine-tuning of plant growth, development, and survival. The present review emphasizes the diversity of sugar signaling integrators, the main molecular and biochemical mechanisms related to the sugar-signaling dependent regulations, and to the regulatory hubs acting in the interplay of the sugar-hormone and sugar-nitrogen networks. It also contributes to compiling evidence likely to fill a few knowledge gaps, and raises new questions for the future.

Exogenous application of GA3 inactively regulates axillary bud outgrowth by influencing of branching-inhibitors and bud-regulating hormones in apple (Malus domestica Borkh.)

Although gibberellin (GA) has been reported to control branching, little is known about how GA mediates signals regulating the outgrowth of axillary buds (ABs). In the current study, the effect of the exogenous application of 5.0 mM GA₃ on ABs outgrowth on 1-year-old 'Nagafu No. 2'/T337/M. robusta Rehd. apple trees was investigated and compared to the bud-activating treatments, 5 mM BA or decapitation. Additionally, the expression of genes related to bud-regulating signals and sucrose levels in ABs was examined. Results indicated that GA₃ did not promote ABs' outgrowth, nor down-regulate the expression of branching repressors [MdTCP40, MdTCP33, and MdTCP16 (homologs of BRANCHED1 and BRC2)], which were significantly inhibited by the BA and decapitation treatments. MdSBP12 and MdSBP18, the putative transcriptional activators of these genes, which are expressed at lower levels in BA-treated and decapitated buds, were up-regulated in the GA₃ treatment in comparison to the BA treatment. Additionally, GA₃ did not up-regulate the expression of CK response- and auxin transport-related genes, which were immediately induced by the BA treatment. In addition, GA₃ also up-regulated the expression of several Tre6P biosynthesis genes and reduced sucrose levels in ABs. Sucrose levels, however, were still higher than what was observed in BA-treated buds, indicating that sucrose may not be limiting in GA₃-controlled AB outgrowth. Although GA₃ promoted cell division, it was not sufficient to induce AB outgrowth. Conclusively, some branching-inhibiting genes and bud-regulating hormones are associated with the inability of GA₃ to activate AB outgrowth.

Developmental control of hypoxia during bud burst in grapevine

Dormant or quiescent buds of woody perennials are often dense and in the case of grapevine (Vitis vinifera L.) have a low tissue oxygen status. The precise timing of the decision to resume growth is difficult to predict, but once committed, the increase in tissue oxygen status is rapid and developmentally regulated. Here, we show that more than a third of the grapevine homologues of widely conserved hypoxia-responsive genes and nearly a fifth of all grapevine genes possessing a plant hypoxia-responsive promoter element were differentially regulated during bud burst, in apparent harmony with resumption of meristem identity and cell-cycle gene regulation. We then investigated the molecular and biochemical properties of the grapevine ERF-VII homologues, which in other species are oxygen labile and function in transcriptional regulation of hypoxia-responsive genes. Each of the 3 VvERF-VIIs were substrates for oxygen-dependent proteolysis in vitro, as a function of the N-terminal cysteine. Collectively, these data support an important developmental function of oxygen-dependent signalling in determining the timing and effective coordination bud burst in grapevine. In addition, novel regulators, including GASA-, TCP-, MYB3R-, PLT-, and WUS-like transcription factors, were identified as hallmarks of the orderly and functional resumption of growth following quiescence in buds.

Distinct gibberellin functions during and after grapevine bud dormancy release

The molecular mechanism regulating dormancy release in grapevine buds is as yet unclear. It has been hypothesized that (i) abscisic acid (ABA) represses bud-meristem activity; (ii) perturbation of respiration induces an interplay between ethylene and ABA metabolism, which leads to removal of repression; and (iii) gibberellin (GA)-mediated growth is resumed. The first two hypothesis have been formally supported. The current study examines the third hypothesis regarding the potential involvement of GA in dormancy release. We found that during natural dormancy induction, levels of VvGA3ox, VvGA20ox, and VvGASA2 transcripts and of GA1 were decreased. However, during dormancy release, expression of these genes was enhanced, accompanied by decreased expression of the bud-expressed GA-deactivating VvGA2ox. Despite indications for its positive role during natural dormancy release, GA application had inhibitory effects on bud break. Hydrogen cyanamide up-regulated VvGA2ox and down-regulated VvGA3ox and VvGA20ox expression, reduced GA1 levels, and partially rescued the negative effect of GA. GA had an inhibitory effect only when applied simultaneously with bud-forcing initiation. Given these results, we hypothesize that during initial activation of the dormant bud meristem, the level of GA must be restricted, but after meristem activation an increase in its level serves to enhance primordia regrowth.

Differential expression of gibberellin- and abscisic acid-related genes implies their roles in the bud activity-dormancy transition of tea plants

Thirty genes involved in GA and ABA metabolism and signalling were identified, and the expression profiles indicated that they play crucial roles in the bud activity-dormancy transition in tea plants. Gibberellin (GA) and abscisic acid (ABA) are fundamental phytohormones that extensively regulate plant growth and development, especially bud dormancy and sprouting transition in perennial plants. However, there is little information on GA- and ABA-related genes and their expression profiles during the activity-dormancy transition in tea plants. In the present study, 30 genes involved in the metabolism and signalling pathways of GA and ABA were first identified, and their expression patterns in different tissues were assessed. Further evaluation of the expression patterns of selected genes in response to GA₃ and ABA application showed that CsGA3ox, CsGA20ox, CsGA2ox, CsZEP and CsNCED transcripts were differentially expressed after exogenous treatment. The expression profiles of the studied genes during winter dormancy and spring sprouting were investigated, and somewhat diverse expression patterns were found for GA- and ABA-related genes. This diversity was associated with the bud activity-dormancy cycle of tea plants. These results indicate that the genes involved in the metabolism and signalling of GA and ABA are important for regulating the bud activity-dormancy transition in tea plants.

In silico analysis of 3 expansin gene promoters reveals 2 hubs controlling light and cytokinins response during bud outgrowth

Bud outgrowth is under the intricate control of environmental and endogenous factors. In a recent paper, ¹ we demonstrated that light perceived by Rosa buds triggers cytokinins (CK) synthesis within 3 hours in the adjacent node followed by their transport to the bud. There, CK control expression of a set of major genes (strigolactones-, auxin-, sugar sink strength-, cells division and elongation-related genes) leading to bud outgrowth in light. Conversely, under dark condition, CK accumulation and transport to the bud are repressed and no bud outgrowth occurs. In this paper, we show that the 3 expansin genes RhEXPA1,2,3 are under the control of both light and CK during bud outgrowth. In silico analysis of promoter sequences highlights 2 regions enriched in light and CK cis-regulatory elements as well as a specific cis-element in pRhEXPA3, potentially responsible for the expression patterns observed in response to CK and light.

Stronger sink demand for metabolites supports dominance of the apical bud in etiolated growth

The potato tuber is a swollen underground stem that can sprout under dark conditions. Sprouting initiates in the tuber apical bud (AP), while lateral buds (LTs) are repressed by apical dominance (AD). Under conditions of lost AD, removal of tuber LTs showed that they partially inhibit AP growth only at the AD stage. Detached buds were inhibited by exogenous application of naphthaleneacetic acid (NAA), whereas 6-benzyladenine (6-BA) and gibberellic acid (GA₃) induced bud burst and elongation, respectively. NAA, applied after 6-BA or GA₃, nullified the latters' growth-stimulating effect in both the AP and LTs. GA₃ applied to the fifth-position LT was transported mainly to the tuber's AP. GA₃ treatment also resulted in increased indole-3-acetic acid (IAA) concentration and cis-zeatin O-glucoside in the AP. In a tuber tissue strip that included two or three buds connected by the peripheral vascular system, treatment of a LT with GA₃ affected only the AP side of the strip, suggesting that the AP is the strongest sink for GA₃, which induces its etiolated elongation. Dipping etiolated sprouts in labeled GA₃ showed specific accumulation of the signal in the AP. Transcriptome analysis of GA₃'s effect showed that genes related to the cell cycle, cell proliferation, and hormone transport are up-regulated in the AP as compared to the LT. Sink demand for metabolites is suggested to support AD in etiolated stem growth by inducing differential gene expression in the AP.

RhVI1 is a membrane-anchored vacuolar invertase highly expressed in Rosa hybrida L. petals

Invertases are a widespread group of enzymes that catalyse the conversion of sucrose into fructose and glucose. Plants invertases and their substrates are essential factors that play an active role in primary metabolism and in cellular differentiation and by these activities they sustain development and growth. Being naturally present in multiple isoforms, invertases are known to be highly differentiated and tissue specific in such a way that every isoform is characteristic of a specific part of the plant. In this work, we report the identification of the invertase RhVI1 that was found to be highly expressed in rose petals. A characterization of this protein revealed that RhVI1 is a glycosylated membrane-anchored protein associated with the cytosolic side of the vacuolar membrane which occurs in vivo in a monomeric form. Purification yields have shown that the levels of expression decreased during the passage of petals from buds to mature and pre-senescent flowers. Moreover, the activity assay indicates RhVI1 to be an acidic vacuolar invertase. The physiological implications of these findings are discussed, suggesting a possible role of this protein during anthesis.

Gibberellin Promotes Shoot Branching in the Perennial Woody Plant Jatropha curcas

Strigolactone (SL), auxin and cytokinin (CK) interact to regulate shoot branching. CK has long been considered to be the only key phytohormone to promote lateral bud outgrowth. Here we report that gibberellin also acts as a positive regulator in the control of shoot branching in the woody plant Jatropha curcas. We show that gibberellin and CK synergistically promote lateral bud outgrowth, and that both hormones influence the expression of putative branching regulators, J. curcas BRANCHED1 and BRANCHED2, which are key transcription factors maintaining bud dormancy. Moreover, treatment with paclobutrazol, an inhibitor of de novo gibberellin biosynthesis, significantly reduced the promotion of bud outgrowth by CK, suggesting that gibberellin is required for CK-mediated axillary bud outgrowth. In addition, SL, a plant hormone involved in the repression of shoot branching, acted antagonistically to both gibberellin and CK in the control of lateral bud outgrowth. Consistent with this, the expression of JcMAX2, a J. curcas homolog of Arabidopsis MORE AXILLARY GROWTH 2 encoding an F-box protein in the SL signaling pathway, was repressed by gibberellin and CK treatment. We also provide physiological evidence that gibberellin also induces shoot branching in many other trees, such as papaya, indicating that a more complicated regulatory network occurs in the control of shoot branching in some perennial woody plants.

Interplay of sugar, light and gibberellins in expression of Rosa hybrida vacuolar invertase 1 regulation

Our previous findings showed that the expression of the Rosa hybrida vacuolar invertase 1 gene (RhVI1) was tightly correlated with the ability of buds to grow out and was under sugar, gibberellin and light control. Here, we aimed to provide an insight into the mechanistic basis of this regulation. In situ hybridization showed that RhVI1 expression was localized in epidermal cells of young leaves of bursting buds. We then isolated a 895 bp fragment of the promoter of RhVI1. In silico analysis identified putative cis-elements involved in the response to sugars, light and gibberellins on its proximal part (595 bp). To carry out functional analysis of the RhVI1 promoter in a homologous system, we developed a direct method for stable transformation of rose cells. 5' deletions of the proximal promoter fused to the uidA reporter gene were inserted into the rose cell genome to study the cell's response to exogenous and endogenous stimuli. Deletion analysis revealed that the 468 bp promoter fragment is sufficient to trigger reporter gene activity in response to light, sugars and gibberellins. This region confers sucrose- and fructose-, but not glucose-, responsive activation in the dark. Inversely, the -595 to -468 bp region that carries the sugar-repressive element (SRE) is required to down-regulate the RhVI1 promoter in response to sucrose and fructose in the dark. We also demonstrate that sugar/light and gibberellin/light act synergistically to up-regulate β-glucuronidase (GUS) activity sharply under the control of the 595 bp pRhVI1 region. These results reveal that the 127 bp promoter fragment located between -595 and -468 bp is critical for light and sugar and light and gibberellins to act synergistically.

Redox regulation of plant development

SIGNIFICANCE

We provide a conceptual framework for the interactions between the cellular redox signaling hub and the phytohormone signaling network that controls plant growth and development to maximize plant productivity under stress-free situations, while limiting growth and altering development on exposure to stress.

RECENT ADVANCES

Enhanced cellular oxidation plays a key role in the regulation of plant growth and stress responses. Oxidative signals or cycles of oxidation and reduction are crucial for the alleviation of dormancy and quiescence, activating the cell cycle and triggering genetic and epigenetic control that underpin growth and differentiation responses to changing environmental conditions.

CRITICAL ISSUES

The redox signaling hub interfaces directly with the phytohormone network in the synergistic control of growth and its modulation in response to environmental stress, but a few components have been identified. Accumulating evidence points to a complex interplay of phytohormone and redox controls that operate at multiple levels. For simplicity, we focus here on redox-dependent processes that control root growth and development and bud burst.

FUTURE DIRECTIONS

The multiple roles of reactive oxygen species in the control of plant growth and development have been identified, but increasing emphasis should now be placed on the functions of redox-regulated proteins, along with the central roles of reductants such as NAD(P)H, thioredoxins, glutathione, glutaredoxins, peroxiredoxins, ascorbate, and reduced ferredoxin in the regulation of the genetic and epigenetic factors that modulate the growth and vigor of crop plants, particularly within an agricultural context.

Light Signaling in Bud Outgrowth and Branching in Plants

Branching determines the final shape of plants, which influences adaptation, survival and the visual quality of many species. It is an intricate process that includes bud outgrowth and shoot extension, and these in turn respond to environmental cues and light conditions. Light is a powerful environmental factor that impacts multiple processes throughout plant life. The molecular basis of the perception and transduction of the light signal within buds is poorly understood and undoubtedly requires to be further unravelled. This review is based on current knowledge on bud outgrowth-related mechanisms and light-mediated regulation of many physiological processes. It provides an extensive, though not exhaustive, overview of the findings related to this field. In parallel, it points to issues to be addressed in the near future.

Genetics and genomics of flower initiation and development in roses

Roses hold high symbolic value and great cultural importance in different societies throughout human history. They are widely used as garden ornamental plants, as cut flowers, and for the production of essential oils for the perfume and cosmetic industries. Domestication of roses has a long and complex history, and the rose species have been hybridized across vast geographic areas such as Europe, Asia, and the Middle East. The domestication processes selected several flower characters affecting floral quality, such as recurrent flowering, double flowers, petal colours, and fragrance. The molecular and genetic events that determine some of these flower characters cannot be studied using model species such as Arabidopsis thaliana, or at least only in a limited manner. In this review, we comment on the recent development of genetic, genomic, and transcriptomic tools for roses, and then focus on recent advances that have helped unravel the molecular mechanisms underlying several rose floral traits.