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For almost a century the plant hormone auxin has been central to theories on apical dominance, whereby the growing shoot tip suppresses the growth of the axillary buds below. According to the classic model, the auxin indole-3-acetic acid is produced in the shoot tip and transported down the stem, where it inhibits bud growth. We report here that the initiation of bud growth after shoot tip loss cannot be dependent on apical auxin supply because we observe bud release up to 24 h before changes in auxin content in the adjacent stem. After the loss of the shoot tip, sugars are rapidly redistributed over large distances and accumulate in axillary buds within a timeframe that correlates with bud release. Moreover, artificially increasing sucrose levels in plants represses the expression of BRANCHED1 (BRC1), the key transcriptional regulator responsible for maintaining bud dormancy, and results in rapid bud release. An enhancement in sugar supply is both necessary and sufficient for suppressed buds to be released from apical dominance. Our data support a theory of apical dominance whereby the shoot tip’s strong demand for sugars inhibits axillary bud outgrowth by limiting the amount of sugar translocated to those buds.

Witches’-broom (WB, excessive initiation, and outgrowth of axillary buds) is one of the remarkable symptoms in plants caused by phytoplasmas, minute wall-less intracellular bacteria. In healthy plants, axillary bud initiation and outgrowth are regulated by an intricate interplay of nutrients (such as sugars), hormones, and environmental factors. However, how these factors are involved in the induction of WB by phytoplasma is poorly understood. We postulated that the WB symptom is a manifestation of the pathologically induced redistribution of sugar and phytohormones. Employing potato purple top phytoplasma and its alternative host tomato (Solanum lycopersicum), sugar metabolism and transportation, and the spatiotemporal distribution of phytohormones were investigated. A transmission electron microscopy (TEM) analysis revealed that starch breakdown was inhibited, resulting in the degradation of damaged chloroplasts, and in turn, premature leaf senescence. In the infected source leaves, two marker genes encoding asparagine synthetase (Sl-ASN) and trehalose-6-phosphate synthase (Sl-TPS) that induce early leaf senescence were significantly up-regulated. However, the key gibberellin biosynthesis gene that encodes ent-kaurene synthase (Sl-KS) was suppressed. The assessment of sugar content in various infected tissues (mature leaves, stems, roots, and leaf axils) indicated that sucrose transportation through phloem was impeded, leading to sucrose reallocation into the leaf axils. Excessive callose deposition and the resulting reduction in sieve pore size revealed by aniline blue staining and TEM provided additional evidence to support impaired sugar transport. In addition, a spatiotemporal distribution study of cytokinin and auxin using reporter lines detected a cytokinin signal in leaf axils where the axillary buds initiated. However, the auxin responsive signal was rarely present in such leaf axils, but at the tips of the newly elongated buds. These results suggested that redistributed sucrose as well as cytokinin in leaf axils triggered the axillary bud initiation, and auxin played a role in the bud elongation. The expression profiles of genes encoding squamosa promoter-binding proteins (Sl-SBP1), and BRANCHED1 (Sl-BRC1a and Sl-BRC1b) that control axillary bud release, as determined by quantitative reverse transcription (qRT)-PCR, indicated their roles in WB induction. However, their interactions with sugars and cytokinins require further study. Our findings provide a comprehensive insight into the mechanisms by which phytoplasmas induce WB along with leaf chlorosis, little leaf, and stunted growth.

Grasses possess basal and aerial axillary buds. Previous studies have largely focused on basal bud (tiller) formation but scarcely touched on aerial buds, which may lead to aerial branch development. Genotypes with and without aerial buds were identified in switchgrass (Panicum virgatum), a dedicated bioenergy crop. Bud development was characterized using scanning electron microscopy. Microarray, RNA-seq and quantitative reverse transcription polymerase chain reaction (RT-qPCR) were used to identify regulators of bud formation. Gene function was characterized by down-regulation and overexpression. Overexpression of miR156 induced aerial bud formation in switchgrass. Various analyses revealed that SQUAMOSA PROMOTER BINDING PROTEIN LIKE4 (SPL4), one of the miR156 targets, directly regulated aerial axillary bud initiation. Down-regulation of SPL4 promoted aerial bud formation and increased basal buds, while overexpression of SPL4 seriously suppressed bud formation and tillering. RNA-seq and RT-qPCR identified potential downstream genes of SPL4. Unlike all previously reported genes acting as activators of basal bud initiation, SPL4 acts as a suppressor for the formation of both aerial and basal buds. The miR156-SPL4 module predominantly regulates aerial bud initiation and partially controls basal bud formation. Genetic manipulation of SPL4 led to altered plant architecture with increased branching, enhanced regrowth after cutting and improved biomass yield.

Common bean (Phaseolus vulgaris L.) plants sprayed with molybdenum (Mo) fertilizer produce Mo‐enriched seeds, which may increase yield in Mo‐poor soils. The challenge has been to produce Mo‐enriched seeds with less fertilizer. Split applications of Mo increase seed Mo content (SMoC), but the number of splits that maximize SMoC has not been studied sufficiently. In three sprinkler‐irrigated field trials, we evaluated the effects of split‐applied Mo fertilizer on SMoC and seed physiological quality. All treatments received NPK fertilizer at sowing. In two treatments, 69 kg ha−1 of urea‐N was top‐dressed or not applied. In six treatments, Na2MoO4·2H2O was foliar‐sprayed once at either 90 or 600 g ha−1 of Mo at the 4th trifoliolate leaf (V4) growth stage, or 600 g ha−1 was split equally at V4 and bud initiation (R5); V4, R5, and full flowering (R6); V4, R5, R6, and early pod formation (R7); or V4, R5, R6, and early and late R7 growth stages. Seed yield for each trial ranged from 3723 to 4621 kg ha−1. Site‐treatment interaction was significant for SMoC and seed germination (p < 0.001). SMoC ranged from 0.11 to 0.23 (only NPK‐fertilized), 1.81 to 3.31 (600 g ha−1, no split), and 5.22 to 6.29 μg (four splits). Four and five splits did not differ significantly for any variable. In two trials, seeds from 600 g ha−1 of Mo had a 3.9% higher germination than seeds from 90 g ha−1. In conclusion, SMoC increases as the number of splits increase up to four times. Additionally, Mo applied at 600 g ha−1 may improve seed germination rate. Core Ideas Seed from NPK‐fertilized plants at sowing and nonsprayed with molybdenum (Mo) had 0.11–0.23 μg of Mo. Plants were sprayed with 600 g ha−1 of Mo or this rate was split into 2–5 applications. Common bean plants sprayed once with 600 g ha−1 produced seed with 1.81–3.31 μg of Mo. Common bean plants sprayed four times produced seed with 5.22–6.29 μg of Mo. The Mo rate of 600 g ha−1 improved seed germination by 3.9 percentage points in two of the three trials.

The seasonal timing of growth events is crucial to tree distribution and conservation. The seasonal growth cycle is strongly adapted to the local climate that is changing because of global warming. We studied bud set as one cornerstone of the seasonal growth cycle in an integrative approach. Bud set was dissected at the phenotypic level into several components, and phenotypic components with most genetic variation were identified. While phenotypic variation resided in the timing of growth cessation, and even so more in the duration from growth cessation to bud set, the timing of growth cessation had a stronger genetic component in both natural and hybrid populations. Quantitative trait loci (QTL) were identified for the most discriminative phenotypic bud-set components across four poplar pedigrees. The QTL from different pedigrees were recurrently detected in six regions of the poplar genome. These regions of 1.83–4.25 Mbp in size, containing between 202 and 394 genes, form the basis for further molecular-genetic dissection of bud set.

European hazelnut ( Corylus avellana L.) micro-propagation enhances the plant materials generation that are true to type and disease free. Here is the response of six hazelnut cvs optimized to standard culture media. The best culture medium from five studied media Murashige and Skoog Medium (MS), Driver and Kuniyuki Medium (DKW), Nas and Read Medium (NRM), modified MS medium (HM), and Woody Plant Medium (WPM), with the optimum concentration of plant growth regulators (PGRs) for six hazelnut cultivars ‘Negret,’ ‘Segorb,’ ‘Ronde de Piemant,’ ‘Fertile de Coutard,’ ‘Merveille de Bollwiller,’ and ‘Long de Espagne’ has been determined. The best results of bud initiation, shoot numbers, number of leaves per bud, leaf area, and survival rate were found in the DKW medium. DKW and MS media supplemented with 4 mgL −1 of 6-Benzylaminopurine (BAP) and 230 µM of Fe-EDDHA were suitable for the initiation phase of single-node explants. Whereas, DKW medium with 25% extra macro- and micro-nutrients, including 5-mgL −1 BAP, and 550-μM Fe-EDDHA was suitable for the shoot proliferation stage. The best shoot elongation was obtained in DKW medium with 30% extra mineral nutrient containing 3-mgL −1 BAP, followed by overlaying with a liquid medium including 0.3-mgL −1 BAP after a couple of weeks. The NRM medium containing only 62.5% of base NRM mineral concentration supplemented with 6-mgL −1 IBA gave the highest rooting rate. The ‘Segorb’ cultivar recorded the best response to in vitro multiplication and the highest survival rate (87.7%) in the greenhouse conditions. This study, presented a modified protocol which improved the efficiency and response of hazelnut cultivars to in vitro propagation.

Summary Branching is a major determinant of crop yield, and enables vigorous shoot growth and the production of a dense canopy. Phytochrome A signal transduction 1 (PAT1) positively regulates phytochrome A signal transduction in response to light, but its effects on branching remain unknown. In this study, we mapped PAT1, and revealed a previously unknown role related to branching and flowering in leafy Brassica juncea. Earlier and increased branching was observed when PAT1 expression was down‐regulated, implying that PAT1 negatively regulates shoot branching. Additionally, down‐regulated PAT1 expression reversed the inhibited branching induced by far‐red light, suggesting PAT1 is involved in the shade avoidance response. PAT1 negatively regulated branching only after bud initiation. The observed interaction between PAT1 and BRC1 implied that PAT1 influences bud outgrowth in a BRC1‐dependent manner. Biochemical and genetic evidence indicate that PAT1 directly interacts with CONSTANS‐LIKE 13 (COL13), which negatively regulates flowering, with the resulting PAT1–COL13 complex mediating shoot branching and flowering. Our findings reveal a new crosstalk modality between phytochrome signalling and flowering pathways during the regulation of shoot branching and flowering. The data presented herein may be useful for future studies involving the editing of the GRAS family transcription factor PAT1 gene to enhance crop productivity and enable earlier harvesting.

Core Ideas Soil salinity could be alleviated by proper use of N fertilizer. No alleviation effect of additional N fertilizer is seen under saline conditions in sunflower's seedling stage. A pot experiment might not be an acceptable substitute for field trail. Soil salinity (S) is one of the most important abiotic stresses limiting crop production in arid and semiarid regions. This study was conducted to investigate the interactive effects of S and nitrogen (N) fertilizer on shoot and root biomass allocation of sunflower (Helianthus annuus L.) at different growth stages. Outdoor field and pot experiments were performed in the Hetao Irrigation District, China. The field study consisted of a 3 × 2 factorial design with three salinity levels (S0: electrical conductivity of a saturated‐paste extract [ECe] = 1.9 dS m−1; S1: ECe = 7.4 dS m−1; S2: ECe = 12.7 dS m−1) and two N application rates (low: 45 kg N ha−1; moderate: 135 kg N ha−1); the S2 treatment was not included in pot study. The results indicated that sunflower allocated more biomass to root under saline conditions in the seedling stage. However, a detrimental effect of moderate N application rate on seedling growth could be found at the S1 level. Moreover, after bud initiation, a moderate N application rate accelerated shoot and root biomass accumulation at the S0 and S1 levels, but it still aggravated salt stress and inhibited sunflower growth at the flowering and mature stages at the S2 level. In addition, our study indicated that the sunflowers planted in pots showed enhanced salt tolerance and decreased the root/shoot ratio earlier than sunflowers planted in fields. We suggest applying less N fertilizer before sowing at both the S1 and S2 levels and using proper additional N fertilizer in the bud stage at the S1 level to promote sunflower growth after salt tolerance has been enhanced.

Eggplant ( Solanum melongena ) is moderately sensitive to salinity. Seed priming and exogenous supplementation are technique that enhances germination, growth, and crop yield by overcoming salt stress. Therefore, this study was designed to understand the role of seed priming and copper (Cu) supplementation in modulating salt tolerance in eggplant. When exposed to salt stress, eggplant seedlings showed significantly higher Na +  content, an increased Na/K ratio, prolonged mean germination time, higher relative water loss, more days to flower bud initiation and first flowering, along with decreased germination rate, growth factors, water content, photosynthetic pigments, ionic contents (K + , Ca 2+ , Mg 2+ ), and yield. The results demonstrated that the germination rate, final germination percentage, germination index, germination energy, and seed vigor index significantly improved, while the mean germination time decreased in Cu-primed seeds. The results also revealed that Cu supplementations increased seedling traits, leaf water content, photosynthetic pigment contents, ionic contents (K + , Ca 2+ , and Mg 2+ ), and yield while decreasing the contents of Na + , and Na/K ratio, mean germination time, relative water loss, days to flower bud initiation, and days to 1st flowering under salt stress. Germination of seeds, seedlings growth traits, plant water status, plant pigments, yield, and ionic contents with the NaCl and Cu treatments were found to substantially interact with each other according to both hierarchical clustering and PCA. Overall, Cu seed priming and exogenous supplementation emerged as a promising strategy to enhance salt tolerance and promote germination, growth, and yield by regulating water status, photosynthetic pigments, and ion homeostasis in eggplant seedlings under NaCl stress. These findings provide valuable insights into the mechanisms of Cu-mediated stress alleviation in eggplant, with implications for sustainable crop production in saline environments.

Background Horn development is a key ruminant trait involving multi-cell type coordination via molecular pathways. This study used scRNA-seq to analyze cellular heterogeneity and fate trajectories during early horn bud niche formation, revealing key gene expression profiles. Combining with hematoxylin–eosin (HE) staining and immunohistochemical analysis, we further verified the asynchronous developmental pathways of key cells in the skin tissue of fetal goat horn bud at induction (embryonic day (E) 50; E50), organogenesis (E60), and cytodifferentiation (E70) stages, and demonstrated the signal transmission routes for the development of early horn buds. Results We revealed temporal and spatial differences of the main signal transmission of horn bud development combining with existing literatures. We speculated that multiple cell types under the guidance of nerve cells collaborated on horn bud initiation in dairy goats. In detail, neural cells receive initial horn bud signals, stimulating hair follicle cell degeneration and transmitting to dermal cells, which evolve through intermediates, amplify signals to epithelial cells, and differentiate into mesenchymal cells. Nerve cell branches also trigger neural crest cell production/migration, working with chondrocytes to promote keratinocyte differentiation for horn bud formation. In addition, we further identified the early horn bud developmental specific events, including the screening of biological functions, signaling pathways and key candidate genes. Conclusions This study employed scRNA-seq to characterize cell fate trajectories and gene expression profiles in goat fetal horn buds. Histological comparisons between hornless and horned fetuses revealed cellular heterogeneity in epithelial, dermal, nerve, and hair follicle cells, with pseudo-time analysis identifying distinct differentiation paths. Dermal and epithelial cell transcriptional dynamics were critical for horn bud initiation (branch 1), supported by immunohistochemistry. Keratinocyte and nerve cell state transitions actively regulated horn development, with asynchronous cell development visualized via immunohistochemistry. Functional enrichment analyses (GO/KEGG) highlighted neural crest development and keratinocyte differentiation pathways, identifying candidate genes ( EGR1 , ZEB2 , SFRP2 , KRT10 , FMOD , CENPW , LDB1 , TWIST1 ) involved in horn morphogenesis. These findings advance understanding of goat horn development and genetic determinants.