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29,582
result(s) for
"shoots"
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Overexpression of OsHMA3 enhances Cd tolerance and expression of Zn transporter genes in rice
Overexpression of a tonoplast-localized transporter, OsHMA3, enhanced Cd tolerance and selectively reduced Cd accumulation in the shoots, but shoot Zn level was maintained by up-regulating genes involved in Zn uptake/translocation.
As a member of the heavy metal ATPase (HMA) family, OsHMA3 is a tonoplast-localized transporter for Cd in the roots of rice (Oryza sativa). Overexpression of OsHMA3 selectively reduces Cd accumulation in the grain. Further characterization in the present study revealed that overexpression of OsHMA3 also enhances the tolerance to toxic Cd. The growth of both the roots and shoots was similar in the absence of Cd between an OsHMA3-overexpressed line and vector control, but the Cd-inhibited growth was significantly alleviated in the OsHMA3-overexpressed line. The overexpressed line showed higher Cd concentration in the roots, but lower Cd concentration in the shoots compared with the wild-type rice and vector control line, indicating that overexpression of OsHMA3 enhanced vacuolar sequestration of Cd in the roots. The Zn concentration in the roots of the OsHMA3-overexpressed line was constantly higher than that of vector control, but the Zn concentration in the shoots was similar between the overexpressed line and vector control. Five transporter genes belonging to the ZIP family were constitutively up-regulated in the OsHMA3-overexpressed line. These results suggest that shoot Zn level was maintained by up-regulating these genes involved in the Zn uptake/translocation. Taken together, overexpression of OsHMA3 is an efficient way to reduce Cd accumulation in the grain and to enhance Cd tolerance in rice.
Journal Article
Exploring key cellular processes and candidate genes regulating the primary thickening growth of Moso underground shoots
The primary thickening growth of Moso (Phyllostachys edulis) underground shoots largely determines the culm circumference. However, its developmental mechanisms remain largely unknown.
Using an integrated anatomy, mathematics and genomics approach, we systematically studied cellular and molecular mechanisms underlying the growth of Moso underground shoots.
We discovered that the growth displayed a spiral pattern and pith played an important role in promoting the primary thickening process of Moso underground shoots and driving the evolution of culms with different sizes among different bamboo species. Different with model plants, the shoot apical meristem (SAM) of Moso is composed of six layers of cells. Comparative transcriptome analysis identified a large number of genes related to the vascular tissue formation that were significantly upregulated in a thick wall variant with narrow pith cavity, mildly spiral growth, and flat and enlarged SAM, including those related to plant hormones and those involved in cell wall development.
These results provide a systematic perspective on the primary thickening growth of Moso underground shoots, and support a plausible mechanism resulting in the narrow pith cavity, weak spiral growth but increased vascular bundle of the thick wall Moso.
Journal Article
Shoot tip necrosis of in vitro plant cultures: a reappraisal of possible causes and solutions
Main conclusion
Shoot tip necrosis is a physiological condition that negatively impacts the growth and development of in vitro plant shoot cultures across a wide range of species.
Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca
2+
) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca
2+
affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca
2+
within a plant, resulting in Ca
2+
deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca
2+
, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitro.
Journal Article
Strigolactone inhibition of shoot branching
A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactonesare compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds andstimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of peaare strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants.Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibitionsignal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis.In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots andact at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching inplants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizalsymbiosis and parasitic weed interaction.
Journal Article
AMT1;1 transgenic rice plants with enhanced NH4+ permeability show superior growth and higher yield under optimal and suboptimal NH4+ conditions
The major source of nitrogen for rice (Oryza sativa L.) is ammonium (NH4(+)). The NH4(+) uptake of roots is mainly governed by membrane transporters, with OsAMT1;1 being a prominent member of the OsAMT1 gene family that is known to be involved in NH4(+) transport in rice plants. However, little is known about its involvement in NH4(+) uptake in rice roots and subsequent effects on NH4(+) assimilation. This study shows that OsAMT1;1 is a constitutively expressed, nitrogen-responsive gene, and its protein product is localized in the plasma membrane. Its expression level is under the control of circadian rhythm. Transgenic rice lines (L-2 and L-3) overexpressing the OsAMT1;1 gene had the same root structure as the wild type (WT). However, they had 2-fold greater NH4(+) permeability than the WT, whereas OsAMT1;1 gene expression was 20-fold higher than in the WT. Analogous to the expression, transgenic lines had a higher NH4(+) content in the shoots and roots than the WT. Direct NH4(+) fluxes in the xylem showed that the transgenic lines had significantly greater uptake rates than the WT. Higher NH4(+) contents also promoted higher expression levels of genes in the nitrogen assimilation pathway, resulting in greater nitrogen assimilates, chlorophyll, starch, sugars, and grain yield in transgenic lines than in the WT under suboptimal and optimal nitrogen conditions. OsAMT1;1 also enhanced overall plant growth, especially under suboptimal NH4(+) levels. These results suggest that OsAMT1;1 has the potential for improving nitrogen use efficiency, plant growth, and grain yield under both suboptimal and optimal nitrogen fertilizer conditions.
Journal Article
The origin and early evolution of vascular plant shoots and leaves
The morphology of plant fossils from the Rhynie chert has generated longstanding questions about vascular plant shoot and leaf evolution, for instance, which morphologies were ancestral within land plants, when did vascular plants first arise and did leaves have multiple evolutionary origins? Recent advances combining insights from molecular phylogeny, palaeobotany and evo–devo research address these questions and suggest the sequence of morphological innovation during vascular plant shoot and leaf evolution. The evidence pinpoints testable developmental and genetic hypotheses relating to the origin of branching and indeterminate shoot architectures prior to the evolution of leaves, and demonstrates underestimation of polyphyly in the evolution of leaves from branching forms in ‘telome theory’ hypotheses of leaf evolution. This review discusses fossil, developmental and genetic evidence relating to the evolution of vascular plant shoots and leaves in a phylogenetic framework.
This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.
Journal Article
CEP family in land plants: evolutionary analyses, expression studies, and role in Arabidopsis shoot development
In Arabidopsis, more than 1000 putative small signalling peptides have been predicted, but very few have been functionally characterized. One class of small post-translationally modified signalling peptides is the C-TERMINALLY ENCODED PEPTIDE (CEP) family, of which one member has been shown to be involved in regulating root architecture. This work applied a bioinformatics approach to identify more members of the CEP family. It identified 10 additional members and revealed that this family only emerged in flowering plants and was absent from extant members of more primitive plants. The data suggest that the CEP proteins form two subgroups according to the CEP domain. This study further provides an overview of specific CEP expression patterns that offers a comprehensive framework to study the role of the CEP signalling peptides in plant development. For example, expression patterns point to a role in aboveground tissues which was corroborated by the analysis of transgenic lines with perturbed CEP levels. These results form the basis for further exploration of the mechanisms underlying this family of peptides and suggest their putative roles in distinct developmental events of higher plants.
Journal Article
Shoot-to-root mobile CEPD-like 2 integrates shoot nitrogen status to systemically regulate nitrate uptake in Arabidopsis
Plants modulate the efficiency of root nitrogen (N) acquisition in response to shoot N demand. However, molecular components directly involved in this shoot-to-root communication remain to be identified. Here, we show that phloem-mobile CEPD-like 2 (CEPDL2) polypeptide is upregulated in the leaf vasculature in response to decreased shoot N status and, after translocation to the roots, promotes high-affinity uptake and root-to-shoot transport of nitrate. Loss of
CEPDL2
leads to a reduction in shoot nitrate content and plant biomass. CEPDL2 contributes to N acquisition cooperatively with CEPD1 and CEPD2 which mediate root N status, and the complete loss of all three proteins severely impairs N homeostasis in plants. Reciprocal grafting analysis provides conclusive evidence that the shoot
CEPDL2
/
CEPD1/2
genotype defines the high-affinity nitrate uptake activity in root. Our results indicate that plants integrate shoot N status and root N status in leaves and systemically regulate the efficiency of root N acquisition.
Plants regulate nitrate uptake in roots to meet nitrogen demand in shoots. Here Ota et al. identify CEPDL2, a polypeptide that is induced during nitrogen deficiency in leaves, and show that it moves via the phloem to promote high-affinity nitrate uptake and root-to-shoot nitrate transport.
Journal Article
Exposure of stevia (Stevia rebaudiana B.) to silver nanoparticles in vitro: transport and accumulation
The impact of nanotechnology in the field of agricultural sciences creates the need to study in greater detail the effect of products offering nanoparticles for application in plant species of agricultural interest. The objective of this study was to determine the response of stevia (
Stevia rebaudiana
B.)
in vitro
to different concentrations of AgNPs (silver nanoparticles), as well as to characterize and identify their absorption, translocation and accumulation mechanisms. Nodal segments of stevia grown in MS medium supplemented with AgNPs (0,12.5, 25, 50,100 and 200 mg L
−1
) were used. After 30 days of
in vitro
shoot proliferation, the number of shoots per explant, shoot length, chlorophyll content, dry matter content and the metallic silver (Ag) content of the plants were quantified. In addition, characterization, transport and accumulation of silver nanoparticles were performed by microscopic analysis. AgNPs were shown to be present in epidermal stem cells, within vascular bundles and in intermembrane spaces. In leaves, they were observed in ribs and stomata. The current and future use of AgNPs in agricultural sciences opens up the possibility of studying their effects on different plant species.
Journal Article