Hormone signalling and root development: an update on the latest Arabidopsis thaliana research

Functional genomics by integrated analysis of transcriptome of sweet potato (Ipomoea batatas (L.) Lam.) during root formation

BACKGROUND

Sweet potato is easily propagated by cuttings. But the molecular biological mechanism of adventitious root formation are not yet clear.

OBJECTIVE

To understand the molecular mechanisms of adventitious root formation from stem cuttings in sweet potato.

METHODS

RNA-seq analysis was performed using un-rooted stem (0 day) and rooted stem (3 days). Gene Ontology (GO) enrichment analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, comparison with Arabidopsis transcription factors (TFs) of DEGs were conducted to investigate the characteristics of genes and TFs involved in root formation. In addition, qRT-PCR analysis using roots at 0, 3, 6, 9, and 12 days after planting was performed to confirm RNA-seq reliability and related genes expression.

RESULTS

42,459 representative transcripts and 2092 DEGs were obtained through the RNA-seq analysis. The DEGs indicated the GO terms related to the single-organism metabolic process and cell periphery, and involved in the biosynthesis of secondary metabolites, and phenylpropanoid biosynthesis in KEGG pathways. The comparison with Arabidopsis thaliana TF database showed that 3 TFs (WRKY, NAC, bHLH) involved in root formation of sweet potato. qRT-PCR analysis, which was conducted to confirm the reliability of RNA-seq analysis, indicated that some metabolisms including oxidative stress and wounding, transport, hormone may be involved in adventitious root formation.

CONCLUSIONS

The detected genes related to secondary metabolism, some hormone (auxin, gibberellin), transports, etc. and 3 TFs (WRKY, NAC, bHLH) may have functions in adventitious roots formation. This results provide valuable resources for future research on the adventitious root formation of sweet potato.

Overview of Sustainable Plant Growth and Differentiation and the Role of Hormones in Controlling Growth and Development of Plants Under Various Stresses

Plant development is different from animals by many fundamental aspects; as they have immobilized cells, a rigid cell wall, and the large central vacuole. Plant growth and cell division are restricted to the specific area of the shoot and root called meristems. Plants have the ability to carry out differentiation, dedifferentiation and redifferentiation. In plants, the growth and differentiation processes are controlled by hormonal and genetic factors. Phytohormones can exert independent/ dependent actions on plant growth and development. A pool of stem cells is placed at the niche of the apex meristem, which is the source of self-renewal of the cell system and its maintenance to provide cells to differentiated tissues. A complex interaction network between hormones and other factors maintains a balance between cell division and differentiation. Auxins promote the growth, gibberellins' function in seed germination, cytokinin's influence on cell division and delay leaf senescence; abscisic acid promotes the stomatal closure and bud dormancy, while salicylic acid promotes resistance against different diseases. Plants are often exposed to different abiotic and biotic stresses, for example, heat, cold, drought, salinity etc., whereas biotic stress arises mainly from fungi, bacteria, insect, etc. Phytohormones play a critical role in well-developed mechanisms that help to perceive the stress signal and enable the plant's optimal growth response. In this review, we studied both the intrinsic and extrinsic factors which govern growth and differentiation of plants under normal and stress condition. This review also deals with genetic modifications occurring in the cell and cell signaling during growth and differentiation.

Different Nanoformulations Alter the Tissue Distribution of Paclitaxel, Which Aligns with Reported Distinct Efficacy and Safety Profiles

Previous studies have shown that different paclitaxel formulations produce distinct anticancer efficacy and safety profiles in animals and humans. This study aimed to investigate the distinct pharmacokinetics and tissue distribution of various nanoformulations of paclitaxel, which may translate into potential differences in safety and efficacy. Four nanoparticle formulations ( nab-paclitaxel, mouse albumin nab-paclitaxel [m -nab-paclitaxel], micellar paclitaxel, and polymeric nanoparticle paclitaxel) as well as solvent-based paclitaxel were intravenously administered to mice. Seventeen blood and tissue samples were collected at different time points. The total paclitaxel concentration in each tissue specimen was measured with liquid chromatography-tandem mass spectrometry. Compared with solvent-based paclitaxel, all four nanoformulations demonstrated decreased paclitaxel exposure in plasma. All nanoformulations were associated with paclitaxel blood-cell accumulation in mice; however, m- nab-paclitaxel was associated with the lowest accumulation. Five minutes after dosing, the total paclitaxel in the tissues and blood was approximately 44% to 57% of the administered dose of all paclitaxel formulations. Paclitaxel was primarily distributed to liver, muscle, intestine, kidney, skin, and bone. Compared with solvent-based paclitaxel, the different nanocarriers altered the distribution of paclitaxel in all tissues with distinct paclitaxel concentration-time profiles. nab-paclitaxel was associated with increased delivery efficiency of paclitaxel in the pancreas compared with the other formulations, consistent with the demonstrated efficacy of nab-paclitaxel in pancreatic cancer. All the nanoformulations led to high penetration in the lungs and fat pad, which potentially points to efficacy in lung and breast cancers. Micellar paclitaxel and polymeric nanoparticle paclitaxel were associated with high paclitaxel accumulation in the heart; thus, the risk of cardiovascular toxicity with these formulations may warrant further investigation. The solvent-based formulation was associated with the poorest paclitaxel penetration in all tissues and the lowest tissue-to-plasma ratio. The different nanocarriers of paclitaxel were associated with distinct pharmacokinetics and tissue distribution, which largely align with the observed efficacy and toxicity profiles in clinical trials.

Getting to the roots of it: Genetic and hormonal control of root architecture

Root system architecture (RSA) - the spatial configuration of a root system - is an important developmental and agronomic trait, with implications for overall plant architecture, growth rate and yield, abiotic stress resistance, nutrient uptake, and developmental plasticity in response to environmental changes. Root architecture is modulated by intrinsic, hormone-mediated pathways, intersecting with pathways that perceive and respond to external, environmental signals. The recent development of several non-invasive 2D and 3D root imaging systems has enhanced our ability to accurately observe and quantify architectural traits on complex whole-root systems. Coupled with the powerful marker-based genotyping and sequencing platforms currently available, these root phenotyping technologies lend themselves to large-scale genome-wide association studies, and can speed the identification and characterization of the genes and pathways involved in root system development. This capability provides the foundation for examining the contribution of root architectural traits to the performance of crop varieties in diverse environments. This review focuses on our current understanding of the genes and pathways involved in determining RSA in response to both intrinsic and extrinsic (environmental) response pathways, and provides a brief overview of the latest root system phenotyping technologies and their potential impact on elucidating the genetic control of root development in plants.

Getting to the roots of it: Genetic and hormonal control of root architecture

Root system architecture (RSA) - the spatial configuration of a root system - is an important developmental and agronomic trait, with implications for overall plant architecture, growth rate and yield, abiotic stress resistance, nutrient uptake, and developmental plasticity in response to environmental changes. Root architecture is modulated by intrinsic, hormone-mediated pathways, intersecting with pathways that perceive and respond to external, environmental signals. The recent development of several non-invasive 2D and 3D root imaging systems has enhanced our ability to accurately observe and quantify architectural traits on complex whole-root systems. Coupled with the powerful marker-based genotyping and sequencing platforms currently available, these root phenotyping technologies lend themselves to large-scale genome-wide association studies, and can speed the identification and characterization of the genes and pathways involved in root system development. This capability provides the foundation for examining the contribution of root architectural traits to the performance of crop varieties in diverse environments. This review focuses on our current understanding of the genes and pathways involved in determining RSA in response to both intrinsic and extrinsic (environmental) response pathways, and provides a brief overview of the latest root system phenotyping technologies and their potential impact on elucidating the genetic control of root development in plants.

Getting to the roots of it: Genetic and hormonal control of root architecture

Root system architecture (RSA) - the spatial configuration of a root system - is an important developmental and agronomic trait, with implications for overall plant architecture, growth rate and yield, abiotic stress resistance, nutrient uptake, and developmental plasticity in response to environmental changes. Root architecture is modulated by intrinsic, hormone-mediated pathways, intersecting with pathways that perceive and respond to external, environmental signals. The recent development of several non-invasive 2D and 3D root imaging systems has enhanced our ability to accurately observe and quantify architectural traits on complex whole-root systems. Coupled with the powerful marker-based genotyping and sequencing platforms currently available, these root phenotyping technologies lend themselves to large-scale genome-wide association studies, and can speed the identification and characterization of the genes and pathways involved in root system development. This capability provides the foundation for examining the contribution of root architectural traits to the performance of crop varieties in diverse environments. This review focuses on our current understanding of the genes and pathways involved in determining RSA in response to both intrinsic and extrinsic (environmental) response pathways, and provides a brief overview of the latest root system phenotyping technologies and their potential impact on elucidating the genetic control of root development in plants.

Root-targeted biotechnology to mediate hormonal signalling and improve crop stress tolerance

Since plant root systems capture both water and nutrients essential for the formation of crop yield, there has been renewed biotechnological focus on root system improvement. Although water and nutrient uptake can be facilitated by membrane proteins known as aquaporins and nutrient transporters, respectively, there is a little evidence that root-localised overexpression of these proteins improves plant growth or stress tolerance. Recent work suggests that the major classes of phytohormones are involved not only in regulating aquaporin and nutrient transporter expression and activity, but also in sculpting root system architecture. Root-specific expression of plant and bacterial phytohormone-related genes, using either root-specific or root-inducible promoters or grafting non-transformed plants onto constitutive hormone producing rootstocks, has examined the role of root hormone production in mediating crop stress tolerance. Root-specific traits such as root system architecture, sensing of edaphic stress and root-to-shoot communication can be exploited to improve resource (water and nutrients) capture and plant development under resource-limited conditions. Thus, root system engineering provides new opportunities to maintain sustainable crop production under changing environmental conditions.