Shoot Growth Research Articles

A computational analysis revealed BES1 transcription factor and β-amylase as crosstalk elements in Upland cotton species (Gossypium sp.)

Cotton is a resilient and multipurpose crop, meeting major of the world’s textile needs while also yielding byproducts like edible oil and animal feed. Starch plays a crucial role in cotton fabric production. It enhances fabric strength by forming a protective film around cotton fibers, making them more resistant to wear and tear. BES1 (brassinosteroid insensitive 1) is a key regulator in brassinosteroid signaling. It controls thousands of target genes involved in development processes. Interestingly, two β-amylase proteins (BAM7 and BAM8) are part of the BES1 family, despite their primary function as β-amylases. β-Amylase (BAM) and BES1 are two gene families with functional and regulatory roles in controlling shoot growth and development by mediating brassinosteroid effects. They share similar domains and participate in various biological processes, tolerance and responses to stresses like salt and drought. In a computational analysis comparing Arabidopsis and Gossypium species, BAM and BES1 were characterized. BES1 genes were grouped into four clusters based on the comparison of the two species. Two clusters corresponded to BAM7 and BAM8, while the other two clusters were associated with BES1. The conserved nucleotide domain sequence is GCTGGATGG. Short tandem repeats include TG and TTG, which can serve as molecular markers. BES1 is specifically linked to cellulose and fiber production and holds promise as a candidate for plant selection and breeding in Gossypium (cotton).

The humic acids influence on the quantity and quality of table grape varieties under the Absheron peninsula conditions

Humates are widely used in viticulture, including ecological viticulture. Humic stuffs benefit the qualitative and quantitative indicators of the grape harvest and can reduce the use of synthetic fertilizers and pesticides. This article presents the results of tests on the foliar application of various doses of the “Rostok” fertilizer in the conditions of the Absheron zone of Azerbaijan on local varieties of table grapes – traditional Tabrizi and a selection variety of Scientific Research Institute of Viticulture and Wine-making Ganjavi, grown in the Ampelographic collection of the institute, located on the Absheron peninsula. Fertilizer was applied in three doses – 0.5; 1.0 and 1.5 liter per hectar. Under the influence of the fertilizer, such elements of yield as the vigor of shoot growth, the number of opened buds, fruitful shoots, the number of berries in a bunch, the weight of a bunch, as well as the sugar content of berry juice increased. Fertilizer application had a positive effect on eliminating signs of leaf chlorosis. No toxic effect on the vegetative organs of the grape plant, on its development, or on the beneficial insect fauna of the vineyard was noted. Based on the data obtained, as well as calculations of economic efficiency, a four-fold application of fertilizer (twice before flowering, once after, once during veraison) at the rate of 1 liter per hectare was recommended for widespread use in wine-growing farms.

Effect of ‘joint cutting’ and positional difference on new shoot growth and uniformity of fruit quality in tree joint training system of Japanese pear ‘Housui’

Effect of ‘joint cutting’ and positional difference on new shoot growth and uniformity of fruit quality in tree joint training system of Japanese pear ‘Housui’

DAYA MULTIPLIKASI EKSPLAN KENTANG AR 8 PADA BERBAGAI KONSENTRASI BENZIL AMINO PURIN (BAP) DAN EKSTRAK BAWANG MERAH DALAM MEDIA DASAR MURASHIGE DAN SKOOG (MS) SECARA IN VITRO

The technique of propagating potato seeds through tissue culture has long been used to produce quality and disease-free seeds. This study aims to test the effect of the combination of BAP and Shallot Extract on the growth of potato plant explants on MS media (Murshige & Skooge). Research in experimental form uses a completely randomized design (CRD) in a factorial pattern consisting of two factors. As the first factor, the growth hormone BAP consists of 4 levels, namely: 0 ppm, 2 ppm, 3 ppm and 4 ppm. Meanwhile, the second factor is: shallot extract consists of 4 treatment levels, namely: 0%, 0.2%, 0.4% and 0.6%. Thus, there were 16 treatment combinations which were repeated 6 times so that the total experimental units were 96. The ABA treatment with a concentration of 2 ppm/liter gave the best effect on the shoot formation time and root formation time of AR 8 potato plant explants. However, the treatment without ABA had a good effect on Shoot length and root length of explant potato plant varieties AR 8. Shallot extract treatment with a concentration of 20% had the best effect on shoot formation time, root formation time, shoot length and number of leaves. However, the treatment with a concentration of 40% had a better effect on the parameters of the number of shoots and the number of explant segments of the AR 8 variety of potato plants. The interaction of the ABA treatment with a concentration of 2 ppm and the shallot extract with a concentration of 20% had the best effect on the time of emergence of shoots and roots on the AR 8 Potato Explants. However, the interaction without ABA (0ppm) and shallot extract had a better effect on the parameters of shoot length, number of leaves, and number of explant segments in the AR 8 potato variety.

Enhancing shoot growth and survival in air-layered pomegranate (Punica granatum L.) var. Super Bhagwa through optimized growth regulator application in Chhattisgarh plain

Enhancing shoot growth and survival in air-layered pomegranate (Punica granatum L.) var. Super Bhagwa through optimized growth regulator application in Chhattisgarh plain

Plant Growth Regulator-based Tissue Culture System Optimization for Cymbidium faberi Rolfe

Cymbidium faberi, a member of the Cymbidium genus known for its fragrant blooms and graceful foliage, has recently become endangered in the wild due to reproductive challenges. This study aimed to establish systematically a tissue culture system for Cymbidium faberi Rolfe (wild species) by evaluating the effects of various plant growth regulators its propagation stages, including rhizome proliferation, differentiation, shoot strengthening, and rooting. The results showed that 0.5 mg·L−1 thidiazuron significantly promoted rhizome proliferation, achieving a proliferation coefficient of 6.08 after 60 days of culture. For adventitious bud induction, 1.92 mg·L−1 brassinolide was most effective, inducing 6.43 buds per rhizome with an average bud height of 5.25 mm after 90 days of culture. The optimal strategy for shoot growth was using 3.0 mg·L−1 1-naphthaleneacetic acid, resulting in an average shoot height of 6.47 cm after 60 days. The highest rooting rate of 87.5% was achieved with 0.5 mg·L−1 zeatin, producing an average of 3.5 roots per shoot with an average root length of 3.06 cm. This study successfully developed a propagation system for C. faberi and highlighted the significant role of BL in promoting rhizome differentiation. In conclusion, this study provides a robust propagation method to support the conservation and industrial development of C. faberi.

Identifying indicators of apple bud dormancy status by exposure to artificial forcing conditions.

Dormancy in temperate fruit trees is a mechanism of temporary growth suspension, which is vital for tree survival during winter. Studies on this phenomenon frequently employ scientific methods that aim to detect the timing of dormancy release. Dormancy release occurs when trees have been exposed to sufficient chill, allowing them to resume growth under conducive conditions. This study investigates dormancy dynamics in two apple (Malus × domestica Borkh.) cultivars, 'Nicoter' and 'Topaz', by sampling branches in an orchard over 14weeks (2019 to 2020) and over 31weeks (2021 to 2022) and subjecting them to a 42-day budbreak forcing period in a growth chamber. Temporal changes in budbreak percentages demonstrated dormancy progression in the studied apple cultivars and allowed the three main dormancy phases to be distinguished: paradormancy (summer dormancy), endodormancy (deep dormancy) and ecodormancy (spring dormancy), along with transition periods between them. Using these data, we explored the suitability of several alternative methods to determine endodormancy release. Tabuenca's test, which predicts dormancy release based on the differences in dry weights of buds with and without forcing, showed promise for this purpose. However, our data indicated a need for considerable adjustments and validation of this test. Bud weight and water content of buds in the orchard did not align with budbreak percentages under forcing conditions, rendering them unsuitable for determining endodormancy release in 'Nicoter' and 'Topaz'. Shoot growth cessation did not seem to be connected with either dormancy progression or dormancy depth of the studied cultivars, whereas leaf fall coincided with the beginning of the transition from endo- to ecodormancy. This work addresses methodological limitations in dormancy research and suggests considering the mean time to budbreak and budbreak synchrony as additional criteria to assess tree dormancy status.

Deciphering physiological and transcriptional mechanisms of maize seed germination.

Maize is a valuable raw material for feed and food production. Healthy seed germination is important for improving the yield and quality of maize. Seed aging occurs relatively fast in crops and it is a process that delays germination as well as reduces its rate and even causes total loss of seed viability. However, the physiological and transcriptional mechanisms that regulate maize seeds, especially aging seed germination remain unclear. Coronatine (COR) which is a phytotoxin produced by Pseudomonas syringae and a new type of plant growth regulator can effectively regulate plant growth and development, and regulate seed germination. In this study, the physiological and transcriptomic mechanisms of COR-induced maize seed germination under different aging degrees were analyzed. The results showed that 0.001-0.01μmol/L COR could promote the germination of aging maize seed and the growth of primary roots and shoots. COR treatment increased the content of gibberellins (GA3) and decreased the content of abscisic acid (ABA) in B73 seeds before germination. The result of RNA-seq analysis showed 497 differentially expressed genes in COR treatment compared with the control. Three genes associated with GA biosynthesis (ZmCPPS2, ZmD3, and ZmGA2ox2), and two genes associated with GA signaling transduction (ZmGID1 and ZmBHLH158) were up-regulated. Three genes negatively regulating GA signaling transduction (ZmGRAS48, ZmGRAS54, and Zm00001d033369) and two genes involved in ABA biosynthesis (ZmVP14 and ZmPCO14472) were down-regulated. The physiological test results also showed that the effects of GA and ABA on seed germination were similar to those of high and low-concentration COR, respectively, which indicated that the effect of COR on seed germination may be carried out through GA and ABA pathways. In addition, GO and KEGG analysis suggested that COR is also highly involved in antioxidant enzyme systems and secondary metabolite synthesis to regulate maize seed germination processes. These findings provide a valuable reference for further research on the mechanisms of maize seed germination.

How do wheat roots improve shoot growth under different local phosphorus supply conditions?

How do wheat roots improve shoot growth under different local phosphorus supply conditions?

Effects of Water and Nitrogen Regulation on Apple Tree Growth, Yield, Quality, and Their Water and Nitrogen Utilization Efficiency.

Apple tree productivity is influenced by the quantity of water and nutrients that are supplied during planting. To enhance resource utilization efficiency and optimize yields, a suitable strategy for supplying water and nitrogen must be established. A field experiment was conducted using a randomized block group design on five-year-old apple trees in Ningxia, with two irrigation lower limit levels (55%FC (W1) and 75%FC (W2)) and four N application levels (0 (N1), 120 (N2), 240 (N3), and 360 (N4) kg·ha-1). Our findings showed that leaf N content increased with a higher irrigation lower limit, but the difference was not statistically significant. However, the leaf N content significantly increased with increasing N application. The growth pattern of new shoots followed logistic curve characteristics, with the maximum new shoot growth rate and time of new shoot growth being delayed under high water and high nitrogen treatments. Apple yield and yield components (weight per fruit and number of fruits per plant) were enhanced under N application compared to no N application. The maximum apple yields were 19,405.3 kg·ha-1 (2022) and 29,607 kg·ha-1 (2023) at the N3 level. A parabolic relationship was observed between apple yield and N application level, with the optimal range of N application being 230-260 kg⸱ha-1. Apple quality indicators were not significantly affected by the irrigation lower limit but were significantly influenced by N application levels. The lower limit of irrigation did not have a significant impact on the quality indicators of the apples. Water and N utilization efficiencies improved with the W2 treatment at the same N application level. A negative relationship was observed between the amount of nitrogen applied and the biased productivity of nitrogen fertilizer. The utilization of nitrogen fertilizer was 127.6 kg·kg-1 (2022) and 200.3 kg·kg-1 (2023) in the W2N2 treatment. The apple yield was sustained, the quality of the fruit improved, and a substantial increase in water productivity was achieved with the W2N3 treatment. The findings of this study can be used as a reference for accurate field irrigation.

Foliar spraying KH2PO4 promotes shoot development by inducing stomatal opening and sugar transport in tea leaves

Tea plant is a perennial woody plant that is mostly harvested for its new shoots. Photoassimilates made from mature leaves are the material basis for the formation of yield and quality of new shoots. Potassium dihydrogen phosphate (KH2PO4) as a common foliar fertilizer has been widely used to improve crop yield and quality formation. However, the effect of KH2PO4 on photosynthesis, photoassimilates formation and transportation in tea plants and underlying molecular mechanism remain unclear. Therefore, in the present study, physiological, metabolomics, and transcriptomics analysis between tea plants spraying KH2PO4 and control were performed. The results showed that spraying KH2PO4 could significantly enhance the growth of new shoots. Further, spraying KH2PO4 could effectively increase the proportion of stomatal opening of mature leaves, and significantly increase net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs). The targeted metabolomics analysis of phloem exudates revealed a significant elevation of sorbitol, arabinitol, d-glucuronic acid, and d-arabinose in mature leaves spraying KH2PO4. Combined with the transcriptome sequencing results, it was found that spraying KH2PO4 significantly induced the up-regulation of genes controlling stomatal opening including HAK17, POT2, ALMT2, ALMT14, PYL4 and PYL2. And the expression levels of photosynthetic antenna proteins such as RA, LHCII type III CAB-13, Lhca3 and LHCI type III LHCA6 were also significantly up-regulated. At last, we found that two polyol transporters, PLT4 and PLT5 were up-regulated. The results revealed the molecular mechanism of KH2PO4 in regulating stomatal opening and the transportation of photoassimilates, laying a theoretical foundation for the application of KH2PO4 in tea plants.

Evaluating the biomedical and environmental safety of selenium nanoparticles synthesized from black pepper seed extract

In recent times, sustainable synthesis of selenium nanoparticles (Se NPs) has seen a significant rise in research, focusing primarily on microbial and plant polysaccharide-based approaches for various bioapplications. However, there are limited studies on the use of extracts from herbal spice plants as capping agents for Se NPs. Therefore, this study investigates the pioneering synthesis of Se NPs using black pepper (Piper nigrum) seed extract (PSe NPs) and assesses their antioxidant properties, hemolytic potential, antibacterial and antibiofilm activities, cytotoxicity, phytotoxicity, in vivo toxicity in zebrafish embryos, and their effectiveness in prolonging the shelf life of food materials. The green-synthesized PSe NPs were thoroughly physicochemically characterized and found to be sphere-shaped with a medium diameter of 10–100 nm. The PSe NPs exhibited substantial antibacterial effects, being more effective against S. aureus (Gram-positive)than against S. typhi (Gram-negative). Furthermore, PSe NPs significantly inhibited MRSA biofilm growth at 500 μg/mL and showed notable antioxidant activity compared to standard gallic acid. Also at 500 μg/mL, PSe NPs induced significant hemolysis, whereas inferior concentrations did not. Cytotoxicity evaluations using the MTT assay revealed that PSe NPs significantly reduced the viability of human normal embryonic kidney (HEK 293) cells and human cervical cancer (HeLa) cells after 24 hours of treatment at concentrations of 0.1–500 μg/mL. This cytotoxic effect was associated with apoptosis, as shown by acridine orange/ethidium bromide staining. In phytotoxicity assays, PSe NPs revealed significant effects on seed germination and root and shoot growth of the mung bean (Vigna radiata). The zebrafish embryotoxicity assay indicated that PSe NPs at 500 µg/mL affected embryo morphology, mortality and survival rates 96 hours after fertilization. Furthermore, the application of PSe NPs gel coatings effectively reduced weight loss and extended the shelf life of fruits such as apples and pears, maintaining their natural appearance.

A novel in vitro shoot excision technique for enhancing proliferation in banana cv. Chini Champa

Micropropagation technology has been commercially exploited for mass multiplication of banana. Several parameters such as nutrient media, explants, culture conditions etc have been standardized. However, a novel in vitro shoot excision technique designed to enhance the proliferation rate of banana cv. Chini Champa has been examined for the first time. We meticulously examined the impact of excision angles (45º and 90º) and excision site (Tip, middle and base) during shoot proliferation stage. Our findings unequivocally demonstrate that employing a 45º angle excision and tip excision yield the highest multiplication rates and biomass accumulation, surpassing other excision angles and methods. The substantial enhancement in shoot numbers, growth and biomass underscores the potential of this technique for improving banana propagation protocols, offering a valuable tool for sustainable banana production.

Toxicity of antimony to plants: Effects on metabolism of N and S in a rice plant

Excess antimony (Sb) has been shown to damage plant growth. Rice plants readily absorb a large amount of Sb after a long period of flooding, yet the mechanisms underlying Sb toxicity in plants have not been solved. This study was conducted to explore the effects of Sb on the uptake of N and S, and monitor the concentrations of reduced glutathione (GSH) and enzymes associated with these processes. In addition, we analyzed differentially expressed metabolites (DEMs) correlated with amino acids (AAs) and oligopeptides, specifically DEMs containing sulfur (S), GSH and indole–3–acetic acid (IAA). The results showed that antimonite [Sb(III)] inhibited shoot growth whereas antimonate [Sb(V)] stimulated shoot growth. Interestingly, Sb(III)5/10 enhanced shoot concentrations of total nitrogen (N), NH4+–N [only at Sb(III)10] and S; but reduced the shoot concentrations of NO3–N and soluble protein. Sb(III)5/10 addition significantly increased oxidized glutathione (GSSG) concentration and activities of glutathione peroxidase (GSH–Px) and glutathione S-transferase (GST) but non–significantly affected concentration of reduced glutathione (GSH) and activities of γ-glutamylcysteine synthetase (GCL) and glutathione reductase (GR), suggesting Sb(III) restricted GSH recycling. Addition of Sb (1) increased the abundance of DEMs associated with lignins, Ca uptake, toxicity/detoxification, and branched chain AAs; (2) decreased the abundance of AAs inclcuding isoleucine (Ile), leucine (Leu), tryptophan (Trp), tyrosine (Tyr) and histidine (His); (3) increased the abundance of arginine (Arg), putrescine (Put) and spermidine (Spd); and (4) affected methylation and acetylation of many AAs, especially acetylation.

Chitin nanofibers promote rhizobial symbiotic nitrogen fixation in Lotus japonicus

Chitin, an N-acetyl-D-glucosamine polymer, has multiple functions in living organisms, including the induction of disease resistance and growth promotion in plants. In addition, chitin oligosaccharides (COs) are used as the backbone of the signaling molecule Nod factor secreted by soil bacteria rhizobia to establish a mutual symbiosis with leguminous plants. Nod factor perception triggers host plant responses for rhizobial symbiosis. In this study, the effects of chitins on rhizobial symbiosis were examined in the leguminous plants Lotus japonicus and soybean. Chitin nanofiber (CNF), retained with polymeric structures, and COs elicited calcium spiking in L. japonicus roots expressing a nuclear-localized cameleon reporter. Shoot growth and symbiotic nitrogen fixation were significantly increased by CNF but not COs in L.japonicus and soybean. However, treatments with chitin and cellulose nanofiber, structurally similar polymers to CNF, did not affect shoot growth and nitrogen fixation in L.japonicus. Transcriptome analysis also supported the specific effects of CNF on rhizobial symbiosis in L.japonicus. Although chitins comprise the same monosaccharides and nanofibers share similar physical properties, only CNF can promote rhizobial nitrogen fixation in leguminous plants. Taking the advantages on physical properties, CNF could be a promising material for improving legume yield by enhancing rhizobial symbiosis.

Fertigation with Nitrogen and Phosphorus Improve Plant Growth, Root Growth, and Buddability of Containerized Citrus Nursery Plants

ABSTRACT Large-scale multiplication of quality planting material is needed to meet the huge demand of planting material in fruit crops. Little information is available on the effect of fertigation on rootstock growth, budding success, and buddling growth in containerized citrus nursery. The present studies were undertaken to study the effect of eight fertigation treatments viz. control (N0P0), N60, N80, N100, N0P100, N60P100, N80P100, and N100P100 on the growth of rough lemon rootstock and subsequently budded three citrus varieties. Among the treatments, N60P100 significantly improved seedling height, diameter, leaf number, root growth, leaf area in rough lemon, Blood Red orange, Kinnow mandarin, and Daisy mandarin over the control. The stomatal conductance was higher with treatments N60, N80, N60P100, and N80P100. While higher photosynthetic rates were observed with N60P100 and N80P100, N60P100 also improved the budding success in Blood Red, Kinnow, and Daisy. Fertigation treatments increased the nutrient concentration in leaves of all the varieties. The principal component analysis revealed that plant height and diameter were positively correlated with root length, root diameter, root number, photosynthetic rate, stomatal conductance, and chlorophyll content in rough lemon. In all the varieties, the sprout length and diameter showed a positive correlation with leaf area, leaf number, root length, root diameter, fibrous root number, photosynthesis rate, stomatal conductance, and chlorophyll content. Among different treatments, N60P100 was the best treatment in improving the shoot growth, root growth, and physiological parameters of rough lemon rootstock. Besides, it also improved budding success and buddling growth in all three citrus varieties.

The Effects of Soil Acidity and Aluminium on the Root Systems and Shoot Growth of Lotus pedunculatus and Lupinus polyphyllus.

Lotus pedunculatus (lotus) and Lupinus polyphyllus (Russell lupin) persist in the upland grasslands of New Zealand, where soil acidity and associated aluminium (Al) toxicity impede conventional pasture legumes. This experiment investigated the response of lotus and Russell lupin to soil acidity and Al. The species were sown in 20 cm tall 1.2 L pots of acidic upland soil. A mass of 4.5 or 6.7 g lime (CaCO3)/L was added to either the top or bottom or both soil horizons (0-9 cm and 9-18 cm), resulting in six treatments across six randomised blocks in a glasshouse. The soil pH was 4.4, 4.9, and 5.4; the exchangeable Al concentrations were 24, 2.5, and 1.5 mg/kg for 0, 4.5, and 6.7 g lime/L. At 16 weeks post-sowing, the plants were divided into shoots and roots at 0-9 cm and 9-18 cm. Root morphology, shoot and root dry matter (DM), shoot nitrogen (N), and nodulation were measured. The total plant DM and shoot-to-root DM ratio were higher, and the shoot %N was lower for the lotus plants than the Russell lupin plants for the various lime rates (13.2 vs. 2.9 g plant-1, 5.6 vs. 1.6, and 2.4 vs. 3.3%, p < 0.05). No response to lime in terms of total DM or total root morphology parameters was exhibited in either species (p > 0.05). Root morphology adjustments in response to acidity between soil horizons were not observed. The results indicated that lotus and Russell lupin are tolerant to high soil acidity (pH 4.4-5.4) and exchangeable Al (1.5-24 mg kg-1), highlighting their considerable adaptation to grasslands with acidic soils.

Spatiotemporal transcriptome atlas reveals gene regulatory patterns during the organogenesis of the rapid growing bamboo shoots.

Bamboo with its remarkable growth rate and economic significance, offers an ideal system to investigate the molecular basis of organogenesis in rapidly growing plants, particular in monocots, where gene regulatory networks governing the maintenance and differentiation of shoot apical and intercalary meristems remain a subject of controversy. We employed both spatial and single-nucleus transcriptome sequencing on 10× platform to precisely dissect the gene functions in various tissues and early developmental stages of bamboo shoots. Our comprehensive analysis reveals distinct cell trajectories during shoot development, uncovering critical genes and pathways involved in procambium differentiation, intercalary meristem formation, and vascular tissue development. Spatial and temporal expression patterns of key regulatory genes, particularly those related to hormone signaling and lipid metabolism, strongly support the hypothesis that intercalary meristem origin from surrounded parenchyma cells. Specific gene expressions in intercalary meristem exhibit regular and dispersed distribution pattern, offering clues for understanding the intricate molecular mechanisms that drive the rapid growth of bamboo shoots. The single-nucleus and spatial transcriptome analysis reveal a comprehensive landscape of gene activity, enhancing the understanding of the molecular architecture of organogenesis and providing valuable resources for future genomic and genetic studies relying on identities of specific cell types.

Overexpression of the ribosome-inactivating protein OsRIP1 modulates the jasmonate signaling pathway in rice.

Ribosome-inactivating proteins (RIPs) are plant enzymes that target the rRNA. The cytoplasmic RIP, called OsRIP1, plays a crucial role in regulating jasmonate, a key plant hormone. Understanding the role of OsRIP1 can provide insights into enhancing stress tolerance and optimizing growth of rice. Transcription profiling by mRNA sequencing was employed to measure the changes in gene expression in rice plants in response to MeJA treatment. Compared to wild type (WT) plants, OsRIP1 overexpressing rice plants showed a lower increase in mRNA transcripts for genes related to jasmonate responses when exposed to MeJA treatment for 3 h. After 24 h of MeJA exposure, the mRNA transcripts associated with the gibberellin pathway occurred in lower levels in OsRIP1 overexpressing plants compared to WT plants. We hypothesize that the mechanism underlying OsRIP1 antagonization of MeJA-induced shoot growth inhibition involves cytokinin-mediated leaf senescence and positive regulation of cell cycle processes, probably via OsRIP1 interaction with 40S ribosomal protein S5 and α-tubulin. Moreover, the photosystem II 10kDa polypeptide was identified to favorably bind to OsRIP1, and its involvement may be attributed to the reduction of photosynthesis in OsRIP1-overexpressing plants subjected to MeJA at the early timepoint (3 h).

At the crossroads: strigolactones mediate changes in cytokinin synthesis and signalling in response to nitrogen limitation.

Strigolactones (SLs) are key regulators of shoot growth and responses to environmental stimuli. Numerous studies have indicated that nitrogen (N) limitation induces SL biosynthesis, suggesting that SLs may play a pivotal role in coordinating systemic responses to N availability, but this idea has not been clearly demonstrated. Here, we generated triple knockout mutants in the SL synthesis gene TaDWARF17 (TaD17) in bread wheat and investigated their phenotypic and transcriptional responses under N limitation, aiming to elucidate the role of SLs in the adaptation to N limitation. Tad17 mutants display typical SL mutant phenotypes, and fail to adapt their shoot growth appropriately to N. Despite exhibiting an increased tillering phenotype, Tad17 mutants continued to respond to N limitation by reducing tiller number, suggesting that SLs are not the sole regulators of tillering in response to N availability. RNA-seq analysis of basal nodes revealed that the loss of D17 significantly altered the transcriptional response of N-responsive genes, including changes in the expression profiles of key N response master regulators. Crucially, our findings suggest that SLs are required for the transcriptional downregulation of cytokinin (CK) synthesis and signalling in response to N limitation. Collectively, our results suggest that SLs are essential for the appropriate morphological and transcriptional adaptation to N limitation in wheat, and that the repressive effect of SLs on shoot growth is partly mediated by their repression of CK synthesis.