Auxin Concentration Research Articles

Multi-omics reveals the metabolic changes and genetic basis of post-flowering rice caryopsis under blue light

BackgroundThe effects of blue light on photosynthetic organs have been studied. However, its effects on non-photosynthetic organs, in particular, on the early stages of rice caryopsis development, are unclear. Thus, we aimed to determine the metabolic characteristics of caryopsis development under blue light to improve the metabolic quality of crop kernels.ResultsWe conducted a multi-omics analysis of each of the three periods from the beginning of cellular differentiation to the end of morphogenesis in post-pollination seeds of a japonica rice variety to explore the effect of blue light on metabolic levels during these metabolic changes and its genetic basis. It was found that blue light caused a gradual decrease in auxin content, a significant increase in the accumulation of JA and flavonoids, and a downregulation of the expression of many starch-related genes and proteins, leads to reduced starch synthesis and smaller starch granules. In addition, the gene co-expression network identified three transcription factors that may regulate starch and two that may regulate flavonoids.ConclusionsIt was found through multi-omics testing that hormones such as jasmonic acid and auxins, and metabolites including alkaloids, flavonoids, lipids, organic acids, phenolic acids, and terpenoids altered significantly. Transcriptome and proteome analyses showed that blue light affected the seed nutrient repository activity. Specifically, starch- and gluten-related genes and proteins were significantly downregulated. Co- and WGCNA analyses identified several transcription factors that were regulated under blue light and identified key regulators of starch. Our study provides an understanding of the effects of blue light on post-flowering development in Gramineae and provides a framework for blue light-induced synthesis of secondary metabolites.Graphical

Genetically Encoded, Noise-Tolerant, Auxin Biosensors in Yeast.

Auxins are crucial signaling molecules that regulate the growth, metabolism, and behavior of various organisms, most notably plants but also bacteria, fungi, and animals. Many microbes synthesize and perceive auxins, primarily indole-3-acetic acid (IAA, referred to as auxin herein), the most prevalent natural auxin, which influences their ability to colonize plants and animals. Understanding auxin biosynthesis and signaling in fungi may allow us to better control interkingdom relationships and microbiomes from agricultural soils to the human gut. Despite this importance, a biological tool for measuring auxin with high spatial and temporal resolution has not been engineered in fungi. In this study, we present a suite of genetically encoded, ratiometric, protein-based auxin biosensors designed for the model yeast Saccharomyces cerevisiae. Inspired by auxin signaling in plants, the ratiometric nature of these biosensors enhances the precision of auxin concentration measurements by minimizing clonal and growth phase variation. We used these biosensors to measure auxin production across diverse growth conditions and phases in yeast cultures and calibrated their responses to physiologically relevant levels of auxin. Future work will aim to improve the fold change and reversibility of these biosensors. These genetically encoded auxin biosensors are valuable tools for investigating auxin biosynthesis and signaling in S. cerevisiae and potentially other yeast and fungi and will also advance quantitative functional studies of the plant auxin perception machinery, from which they are built.

A protocol for the development and maintenance of Coffea arabica (L.) cell suspension cultures

Coffea spp. are remarkable sources of phytochemicals, but the lack of a well-defined culture medium aimed at the induction of non-embryogenic and friable callus hampers the establishment of plant cell suspension cultures for large-scale production of valuable compounds. In this paper, we describe a one-medium protocol suitable to obtain both callus and cell suspension cultures from leaves of two elite cultivars of C. arabica. The protocol was developed through an iterative process involving the determination of the best concentration of auxin and cytokinin, their optimal ratio, as well as the most effective molecule of either hormone class. Young leaves were found to be a good and easy-to-use explant source for callus induction and proliferation, provided that a cytokinin was present in association with a chlorinated auxin in a full strength, semi-solid MS medium. The best results were obtained by hormone concentration and combination of 1 mg/L of both kinetin and 2,4,5-trichlorophenoxyacetic acid. The same ratio of these growth regulators was conveniently used for the development and stabilization of cell suspension cultures in liquid MS medium. When grown in darkness, stabilized suspension cultures showed a fine and homogeneous texture, with a 10-fold biomass increase within 25 days and a cell viability > 90%. In addition, the phytochemical profile revealed the presence of the most widely studied coffee compounds. The protocol can be applied to obtain adequate amounts of cell biomass for use in physiological studies concerning the production of secondary metabolites.

Gβγ dimers mediate low K+ stress-inhibited root growth via modulating auxin redistribution in Arabidopsis.

In the investigation of heterotrimeric G protein-mediated signal transduction in planta, their roles in the transmittance of low K+ stimuli remain to be elucidated. Here, we found that the primary root growth of wild-type Arabidopsis was gradually inhibited with the decrease of external K+ concentrations, while the primary root of the mutants for G protein β subunit AGB1 and γ subunits AGG1, AGG2 and AGG3 could still grow under low K+ conditions (LK). Exogenous NAA application attenuated primary root elongation in agb1 and agg1/2/3 but promoted the growth in wild-type seedlings under LK stress. Using ProDR5:GFP, ProPIN1:PIN1-GFP and ProPIN2:PIN2-GFP reporter lines, a diminishment in auxin concentration at the radicle apex and a reduction in PIN1and PIN2 efflux carrier abundance were observed in wild-type roots under LK, a phenomenon not recorded in the agb1 and agg1/2/3. Further proteolytic and transcriptional assessments revealed an enhanced degradation of PIN1 and a suppressed expression of PIN2 in the wild-type background under LK, contrasting with the stability observed in the agb1 and agg1/2/3 mutants. Our results indicate that the G protein β and γ subunits play pivotal roles in suppressing of Arabidopsis root growth under LK by modulating auxin redistribution via alterations in PIN1 degradation and PIN2 biosynthesis.

Genome-wide analysis of Citrus medica ABC transporters reveals the regulation of fruit development by CmABCB19 and CmABCC10

ATP-binding cassette (ABC) transporters are vital for plant growth and development as they facilitate the transport of essential molecules. Despite the family's significance, limited information exists about its functional distinctions in Citrus medica. Our study identified 119 genes encoding ABC transporter proteins in the C. medica genome. Through an evolutionary tree and qPCR analysis, two ABC genes, CmABCB19 and CmABCC10, were implicated in C. medica fruit development, showing upregulation in normal fruits compared to malformed fruits. CmABCB19 was found to localize to the plasma membrane of Nicotiana tabacum, exhibiting indole-3-acetic acid (IAA) efflux activity in the yeast mutant strain yap1. CmABCC10, a tonoplast-localized transporter, exhibited efflux of diosmin, nobiletin, and naringin, with rutin influx in strain ycf1. Transgenic expression of CmABCB19 and CmABCC10 in Arabidopsis thaliana induced alterations in auxin and flavonoid content, impacting silique and seed size. This effect was attributed to the modulation of structural genes in the auxin biosynthesis (YUC5/9, CYP79B2, CYP83B1, SUR1) and flavonoid biosynthesis (4CL2/3, CHS, CHI, FLS1/3) pathways. In summary, the functional characterization of CmABCB19 and CmABCC10 illuminates auxin and flavonoid transport, offering insights into their interplay with biosynthetic pathways and providing a foundation for understanding the transporter's role in fruit development.

Overexpression of MtIPT gene enhanced drought tolerance and delayed leaf senescence of creeping bentgrass (Agrostis stolonifera L.)

BackgroundIsopentenyltransferases (IPT) serve as crucial rate-limiting enzyme in cytokinin synthesis, playing a vital role in plant growth, development, and resistance to abiotic stress.ResultsCompared to the wild type, transgenic creeping bentgrass exhibited a slower growth rate, heightened drought tolerance, and improved shade tolerance attributed to delayed leaf senescence. Additionally, transgenic plants showed significant increases in antioxidant enzyme levels, chlorophyll content, and soluble sugars. Importantly, this study uncovered that overexpression of the MtIPT gene not only significantly enhanced cytokinin and auxin content but also influenced brassinosteroid level. RNA-seq analysis revealed that differentially expressed genes (DEGs) between transgenic and wild type plants were closely associated with plant hormone signal transduction, steroid biosynthesis, photosynthesis, flavonoid biosynthesis, carotenoid biosynthesis, anthocyanin biosynthesis, oxidation-reduction process, cytokinin metabolism, and wax biosynthesis. And numerous DEGs related to growth, development, and stress tolerance were identified, including cytokinin signal transduction genes (CRE1, B-ARR), antioxidase-related genes (APX2, PEX11, PER1), Photosynthesis-related genes (ATPF1A, PSBQ, PETF), flavonoid synthesis genes (F3H, C12RT1, DFR), wax synthesis gene (MAH1), senescence-associated gene (SAG20), among others.ConclusionThese findings suggest that the MtIPT gene acts as a negative regulator of plant growth and development, while also playing a crucial role in the plant’s response to abiotic stress.

Different viral effectors hijack TCP17, a key transcription factor for host Auxin synthesis, to promote viral infection.

Auxin is an important class of plant hormones that play an important role in plant growth development, biotic stress response, and viruses often suppress host plant auxin levels to promote infection. However, previous research on auxin-mediated disease resistance has focused mainly on signaling pathway, and the molecular mechanisms of how pathogenic proteins manipulate the biosynthetic pathway of auxin remain poorly understood. TCP is a class of plant-specific transcription factors, of which TCP17 is a member that binds to the promoter of YUCCAs, a key rate-limiting enzyme for auxin synthesis, and promotes the expression of YUCCAs, which is involved in auxin synthesis in plants. In this study, we reported that Tomato spotted wilt virus (TSWV) infection suppressed the expression of YUCCAs through its interaction with TCP17. Further studies revealed that the NSs protein encoded by TSWV disrupts the dimerization of TCP17, thereby inhibit its transcriptional activation ability and reducing the auxin content in plants. Consequently, this interference inhibits the auxin response signal and promotes the TSWV infection. Transgenic plants overexpressing TCP17 exhibit resistance against TSWV infection, whereas plants knocking out TCP17 were more susceptible to TSWV infection. Additionally, proteins encoded by other RNA viruses (BSMV, RSV and TBSV) can also interact with TCP17 and interfere with its dimerization. Notably, overexpression of TCP17 enhanced resistance against BSMV. This suggests that TCP17 plays a crucial role in plant defense against different types of plant viruses that use viral proteins to target this key component of auxin synthesis and promote infection.

Effect of cutting age and auxin concentration on growth of pinto peanut (Arachis pintoi)

Pinto peanuts are known as versatile cover crops for soil conservation, biomulch, and ornamental plants. These plants rarely produce seeds, so they are commonly propagated vegetatively, resulting in low efficiency of seedling production and availability of cuttings. The aim of this study was to determine the effect of cutting age and auxin application on the growth of pinto peanut. This experiment used a complete randomized block factorial design. The first factor was the age of the cuttings (stolons) with three levels (young, intermediate, old). Each cutting had three nodes, with young cuttings measured from the tip, intermediate cuttings measured from the fourth node, and old cuttings measured from the seventh node. The second factor was the concentration of the commercial auxin product ROOTONE F (0 ppm, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm). The results showed that the difference in cutting age significantly affected the number of leaves (at 10 and 50 days after planting), plant length (at 10 to 50 days after planting), number of branches (at 30 to 50 days after planting), and canopy area. Differences in auxin concentration only significantly affected plant length from 10 to 30 days after planting. The interaction between cutting age and auxin concentration was significant only for the number of leaves at 10 to 20 days after planting and plant length at 50 days after planting. The highest values for the observed parameters were consistently obtained by intermediate cuttings, which are therefore recommended as planting material for ornamental peanut cuttings.

In-vitro Regeneration of An Endangered Medicinal Plant Anodendron paniculatum (Apocynaceae)

Objectives: The present study aims to establish a standardized and efficient regeneration protocol for Anodendron paniculatum A. DC. (Apocynaceae) by optimizing the effect of various plant growth regulators as it is categorized globally as an endangered medicinal plant. Methods: MS medium fortified with 3% sucrose (w/v) and different concentrations of cytokinins 6-benzylamino purine (BAP), kinetin, thidiazuron either alone or in combination with auxins, indole 3-acetic acid (IAA), naphthalene acetic acid (NAA) and GA3. For the in vitro root induction, individual and healthy shoots (3-4 cm in length) were excised in the 7th week and were cultured onto basal and half-strength MS medium supplemented with various concentrations of auxins and incubated in the culture room. Findings: MS medium supplemented with thidiazuron (2.5 𝜇M) in combination with indole 3-acetic acid (2.5 𝜇M) and GA3 (1.25 𝜇M) was most effective, providing multiple shoot regeneration for 79.33% of cotyledonary leaf explants associated with a high number of shoots per explant (20.00 ± 1.15) and length of shoot (2.66 ± 0.08 cm). Whereas, the frequency of response, mean number of shoots, and respective lengths were varied with different concentrations of 6-benzylamino purine when used in combination with IAA or NAA and BAP (5.0 𝜇M) along with IAA (2.5 𝜇M) at the frequency of 47.66%. Whereas, the addition of GA3 (1.25 𝜇M) in combination with BAP (5.0 𝜇M) and IAA (2.5 𝜇M) has shown a maximum number of multiple shoot formation/explant (12.33) with length of shoot (1.53 ± 0.08 cm). MS medium supplemented with 10 𝜇M 6-benzyl amino purine and 2.5 𝜇M naphthalene acetic acid recorded the highest response (53.66%) with more number of the shoot (9.66) and length of the shoot (1.83 ± 0.03 cm) per explant. The maximum percentage of response (84.33%) was recorded at 1 2 strength MS medium with 5.0 𝜇M NAA, whereas the highest number of roots per shoot (6.66 ± 0.33) was induced at MS + 5.0 𝜇M NAA. The highest length of roots (3.66 cm) was recorded at basal MS medium fortified with 5.0 𝜇M NAA and 7.5 𝜇M NAA. Novelty: The standardized protocol method is of first of its kind, a quick and suitable approach for the high quantity production of Anodendron paniculatum with appropriate concentrations of plant growth regulators that meet thecommercial demand of endangered medicinal plants. Keywords: Anodendron paniculatum; Endangered plant; Plant growth regulators; Regeneration; Protocol standardization

A QTL GN1.1, encoding FT-L1, regulates grain number and yield by modulating polar auxin transport in rice.

Rice grain number is a crucial agronomic trait impacting yield. In this study, we characterized a quantitative trait locus (QTL), GRAIN NUMBER 1.1 (GN1.1), which encodes a Flowering Locus T-like1 (FT-L1) protein and acts as a negative regulator of grain number in rice. The elite allele GN1.1B, derived from the Oryza indica variety, BF3-104, exhibits a 14.6% increase in grain yield compared with the O. japonica variety, Nipponbare, based on plot yield tests. We demonstrated that GN1.1 interacted with and enhanced the stability of ADP-ribosylation factor (Arf)-GTPase-activating protein (Gap), OsZAC. Loss of function of OsZAC results in increased grain number. Based on our data, we propose that GN1.1B facilitates the elevation of auxin content in young rice panicles by affecting polar auxin transport (PAT) through interaction with OsZAC. Our study unveils the pivotal role of the GN1.1 locus in rice panicle development and presents a novel, promising allele for enhancing rice grain yield through genetic improvement.

In vitro micropropagation and mass multiplication of Stevia rebaudiana Bertoni

Stevia rebaudiana Bertoni, an ancient perennial herb produces steviol glycosides including stevioside and rebaudioside-A that are valuable as low calorie sweeteners, about 300-400 times sweeter than saccharose. Conventional propagation methods are not produce adequate planting material. Micro propagation is an imperative technology that could be extensively exploited to meet the growing demands of elite planting material for commercially cultivated. The prime objective of this study was to established standard protocol for in vitro regeneration and mass multiplication in Stevia. In present investigation, different concentrations of Auxin and Cytokinin were tried for optimization of shoot initiation, shoot multiplication, root initiation and callus induction of Stevia from different explant. BAP and IBA (1.0+0.5) mg/l, IBA (2.0) mg/l shows promising results of shoot multiplication and root initiation respectively.

Insights into the ameliorative effect of ZnONPs on arsenic toxicity in soybean mediated by hormonal regulation, transporter modulation, and stress responsive genes.

Arsenic (As) contamination of agricultural soils poses a serious threat to crop productivity and food safety. Zinc oxide nanoparticles (ZnONPs) have emerged as a potential amendment for mitigating the adverse effects of As stress in plants. Soybean crop is mostly grown on marginalized land and is known for high accumulation of As in roots than others tissue. Therefore, this study aimed to elucidate the underlying mechanisms of ZnONPs in ameliorating arsenic toxicity in soybean. Our results demonstrated that ZnOB significantly improved the growth performance of soybean plants exposed to arsenic. This improvement was accompanied by a decrease (55%) in As accumulation and an increase in photosynthetic efficiency. ZnOB also modulated hormonal balance, with a significant increase in auxin (149%), abscisic acid (118%), gibberellin (160%) and jasmonic acid content (92%) under As(V) stress assuring that ZnONPs may enhance root growth and development by regulating hormonal signaling. We then conducted a transcriptomic analysis to understand further the molecular mechanisms underlying the NPs-induced As(V) tolerance. This analysis identified genes differentially expressed in response to ZnONPs supplementation, including those involved in auxin, abscisic acid, gibberellin, and jasmonic acid biosynthesis and signaling pathways. Weighted gene co-expression network analysis identified 37 potential hub genes encoding stress responders, transporters, and signal transducers across six modules potentially facilitated the efflux of arsenic from cells, reducing its toxicity. Our study provides valuable insights into the molecular mechanisms associated with metalloid tolerance in soybean and offers new avenues for improving As tolerance in contaminated soils.

Karrikinolide1 (KAR1), a Bioactive Compound from Smoke, Improves the Germination of Morphologically Dormant Apium graveolens L. Seeds by Reducing Indole-3-Acetic Acid (IAA) Levels.

Smoke-water (SW) and Karrikinolide1 (KAR1) release dormancy and improve seed germination in many plant species. Therefore, we tested SW (1:2500 v/v) and KAR1 (10-7 M) to break the morphological dormancy of celery cultivar (Apium graveolens L.). In the first trial, seeds were subjected to a 21-day incubation period at 20 °C with SW and KAR1 applied as single treatments. KAR1 showed significantly improved germination (30.7%) as compared to SW (17.2%) and a water control (14.7%). In seed soaking experiments, SW, KAR1, and gibberellic acid (GA3) treatments showed higher germination percentages than the water control after 3 and 6 h of soaking. However, prolonged soaking (12 h) reduced germination percentages for all treatments, indicating a detrimental effect. Analysis of KAR1 content dynamics in 7-day- and 21-day-old celery seeds indicated its prolonged effects on germination and dormancy alleviation. Phytohormones, including auxins in 7-day-old and cytokinins in 7-day- and 21-day-old celery seedlings, along with their precursors and metabolites, were analyzed using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) after treatment with KAR1 and SW. The analysis of auxin levels in 7-day-old seeds revealed a negative correlation between seed germination and auxin (indole-3-acetic acid, IAA) content. Notably, it was found that KAR1-treated seeds significantly reduced IAA levels in all treatments. SW and KAR1 did not significantly affect cytokinin levels during celery germination except for N6-Isopentenyladenine. Hence, further research is needed to understand their precise role in celery seed germination. This work will improve our understanding of the role of bioactive compounds from plant-derived smoke and how they regulate hormonal responses and improve germination efficiency in celery.

LATA1, a RING E3 ligase, modulates the tiller angle by affecting auxin asymmetric distribution and content in rice.

The tiller angle is an important agronomic trait that determines plant architecture and grain yield in rice (Oryza sativa L.). However, the molecular regulation mechanism of the rice tiller angle remains unclear. Here, we identified a rice tiller angle gene, LARGE TILLER ANGLE 1 (LATA1), using the MutMap approach. LATA1 encodes a C3H2C3-type RING zinc finger E3 ligase and the conserved region of the RING zinc finger is essential for its E3 activity. LATA1 was highly expressed in the root and tiller base and LATA1-GFP fusion protein was specifically localized to the nucleus. The mutation of LATA1 significantly reduced indole-3-acetic acid content and attenuated lateral auxin transport, thereby resulting in defective shoot gravitropism and spreading plant architecture in rice. Further investigations found that LATA1 may indirectly affect gravity perception by modulating the sedimentation rate of gravity-sensing amyloplasts upon gravistimulation. Our findings provide new insights into the molecular mechanism underlying the rice tiller angle and new genetic resource for the improvement of plant architecture in rice.

Activation of the antioxidant system and transduction of the mediated by exogenous calcium improve drought resistance in tobacco

Drought stress is one of the most important stresses in plants. The important role of calcium signal as a second messenger in alleviating drought stress is still unclear. We used tobacco as test material to simulate drought stress with 20 % PEG concentration. Physiological and transcriptome techniques were used to study how the model plant tobacco protects itself from drought stress by examining the mechanism used by exogenous calcium ions to respond to the antioxidant and hormone signals that indicate drought stress. Exogenous calcium was shown to increase the levels of expression of the proteins CDPK, CBL/CIPK and AQPs that respond to signaling by calcium under drought stress. The cis-acting elements of the promoters of the genes related to signals primarily focused on hormone and drought-related elements, which suggests that the exogenous calcium may mediate the transduction of hormone signals in response to drought stress. The results of physiological and transcriptional data showed that oxidative damage occurred in the tobacco leaves under drought stress. Under drought stress, exogenous calcium can enhance the activities of SOD (4.75 %), POD (42.33 %) and APX (512.43 %), up-regulate the expression of the genes that encode antioxidant enzymes to eliminate excessive reactive oxygen species (ROS), and alleviate the oxidative damage to tobacco leaves under drought stress. The calcium produced during drought stress increased the content of auxin (IAA), decreased that of abscisic acid (ABA) and downstream gene expression, and prevented excessive amplification of the ABA signal. Exogenous calcium enhanced the crosstalk between cytokinin, gibberellin and ABA signals.In summary, exogenous calcium can stimulate the synergistic effect of calcium and hormone signals and the antioxidant system, eliminate ROS, improve the crosstalk between plant hormones, and improve the drought resistance of tobacco.

Chitosan (CTS) induced secondary metabolite production in Canscora decussata Schult. - An endangered medicinal plant

Bioengineering has excellent potential in plant-based in vitro cultures for efficiently synthesizing desired plant products. Due to the rapid destruction of natural habitats, in vitro methods might save endangered species. Winged-Stem Canscora is an endangered medicinal herb used in traditional medicine for brain disorders. This study investigates the induction of in-vitro metabolite production using chitosan. Among the various concentrations of auxins tested, 82% of callus was obtained from Murashige and Skoog (MS) medium with 3 mg L−1 Kinetin (KIN) + 1 mg L−1 1-Naphthaleneacetic acid (NAA). The highest callus content was after the 3rd subculture at 200 mg L−1 chitosan treatment. On the 70th day of culture, levels of total phenolics and flavonoids are increased in the elicited and normal callus. However, antioxidant activity was higher in elicited callus compared to normal callus and wild plants. Higher secondary metabolite concentrations of elicited callus have superior anti-bacterial and anti-fungal activity. Secondary metabolites from elicited callus have a lower inhibitory concentration than those from wild plant and normal callus. High-performance thin layer chromatography (HPTLC) analysis showed that the elicited callus had higher amounts of mangiferin (0.178 μg mL−1) and scopoletin (0.133 μg mL−1). An efficient approach was employed to ensure that sufficient amounts of the widely used plant secondary metabolites from medicinal plants, such as mangiferin and scopoletin, were accessible to meet demand.

High-Efficiency In Vitro Root Induction in Pear Microshoots (Pyrus spp.).

Extensive research has been conducted on the in vitro mass propagation of pear (Pyrus spp.) trees through vegetative propagation, demonstrating high efficiency in shoot multiplication across various pear species. However, the low in vitro rooting rates remain a significant barrier to the practical application and commercialization of mass propagation. This study aims to determine the favorable conditions for inducing root formation in the in vitro microshoots of Pyrus genotypes. The base of the microshoots was exposed to a high concentration (2 mg L-1) of auxins (a combination of IBA and NAA) for initial root induction at the moment when callus formation begins. The microshoots were then transferred to an R1 medium (1/2 MS with 30 g L-1 sucrose without PGRs) to promote root development. This method successfully induced rooting in three European pear varieties, one Asian pear variety, and a European-Asian hybrid, resulting in rooting rates of 66.7%, 87.2%, and 100% for the European pear (P. communis), 60% for the Asian pear (P. pyrifolia), and 83.3% for the hybrid pear (P. pyrifolia × P. communis) with an average of 25 days. In contrast, the control group (MS medium) exhibited rooting rates of 0-13.3% after 60 days of culture. These findings will enhance in vitro root induction for various pear varieties and support the mass propagation and acclimatization of pear. The in vitro root induction method developed in this study has the potential for global commercial application in pear cultivation.

Selenite improves growth by modulating phytohormone pathways and reprogramming primary and secondary metabolism in tomato plants

Selenium (Se) is an essential micronutrient in organisms that has a significant impact on physiological activity and gene expression in plants, thereby affecting growth and development. Humans and animals acquire Se from plants. Tomato (Solanum lycopersicum L.) is an important vegetable crop worldwide. Improving the Se nutrient level not only is beneficial for growth, development and stress resistance in tomato plants but also contributes to improving human health. However, the molecular basis of Se-mediated tomato plant growth has not been fully elucidated. In this study, using physiological and transcriptomic analyses, we investigated the effects of a low dosage of selenite [Se(Ⅳ)] on tomato seedling growth. Se(IV) enhanced the photosynthetic efficiency and increased the accumulation of soluble sugars, dry matter and organic matter, thereby promoting tomato plant growth. Transcriptome analysis revealed that Se(IV) reprogrammed primary and secondary metabolic pathways, thus modulating plant growth. Se(IV) also increased the concentrations of auxin, jasmonic acid and salicylic acid in leaves and the concentration of cytokinin in roots, thus altering phytohormone signaling pathways and affecting plant growth and stress resistance in tomato plants. Furthermore, exogenous Se(IV) alters the expression of genes involved in flavonoid biosynthesis, thereby modulating plant growth and development in tomato plants. Taken together, these findings provide important insights into the regulatory mechanisms of low-dose Se(IV) on tomato growth and contribute to the breeding of Se-accumulating tomato cultivars.

Effect of auxin on in vitro rooting of the triploid Musa paradisiaca L. cv. Nendran (AAB)

Banana is an important fruit crops of the family Musaceae. Tissue culture multiplication of banana is now popular and preferred due to faster multiplication, uniformly and cost-effective production of healthy planting materials. The following work was take on to study the result of various concentrations of auxin (indole-3-butyric acid-IBA). Shoots derived from sucker explants after a series of multiplication (4 to 5), regenerated plants having 4.5 cm length were dissected out and rooted in different concentrations of auxin (IBA) (0.5 to 3.5 mg/L). Root production was started after 10 days of culture and the data taken after 20 days. From all the treatment tested all media concentrations produce roots at varied level with in a period of 15-20 days of culture. Media having concentrations of IBA were used to induce in vitro rooting in plantlets of Musa cv. Nendran after six sub cultures including elongation. The elongated shoots harvested from culture bottles were transferred to MS solid media supplemented with auxin IBA at varied concentrations. The root induction rate varied from one media concentration to another. The present study revealed that IBA (1.0 mg/L) was found to be most applicable hormone for root induction in sucker shoot tip explants of Musa cv. Nendran.

Effect of Spraying with Different Types and Concentrations of Auxin and Two Growth Stages of the Date Palm (Al-Sultani cultivar) on the Chemical Traits of the Leaves and the Amount of Yield

Effect of Spraying with Different Types and Concentrations of Auxin and Two Growth Stages of the Date Palm (Al-Sultani cultivar) on the Chemical Traits of the Leaves and the Amount of Yield