X-ray fluorescence spectroscopy (XRF) is an analytical tool used to determine the elemental composition in a myriad of sample matrices. Due to the XRF non-destructive feature, this technique may ...allow time-resolved plant tissue analyses under in vivo conditions, and additionally, the combination with other non-destructive techniques. In this study, we employed handheld and benchtop XRF to evaluate the elemental distribution changes in living plant tissues exposed to X-rays, as well as real-time uptake kinetics of Zn(aq) and Mn(aq) in soybean (Glycine max (L.) Merrill) stem and leaves, for 48 hours, combined with transpiration rate assessment on leaves by an infrared gas analyzer (IRGA). We found higher Zn content than Mn in stems. The latter micronutrient, in turn, presented higher concentration in leaf veins. Besides, both micronutrients were more concentrated in the first trifolium (i.e., youngest leaf) of soybean plants. Moreover, the transpiration rate was more influenced by circadian cycles than Zn and Mn uptake. Thus, XRF represents a convenient tool for in vivo nutritional studies in plants, and it can be coupled successfully to other analytical techniques.
Strains of
Bacillus thuringiensis
(
Bt
) are commonly commercialized as bioinoculants for insect pest control, but their benefits go beyond their insecticidal property: they can act as plant ...growth-promoters. Auxins play a major role in the plant growth promotion. However, the mechanism of auxin production by the Bacilli group, and more specifically by
Bt
strains, is unclear. In previous work, the plant growth-promoting rhizobacterium (PGPR)
B. thuringiensis
strain RZ2MS9 increased the corn roots. This drew our attention to the strain’s auxin production trait, earlier detected in vitro. Here, we demonstrate that in its genome, RZ2MS9 harbours the complete set of genes required in two pathways that are used for Indole acetic acid (IAA) production. We also detected that the strain produces almost five times more IAA during the stationary phase. The bacterial application increased the shoot dry weight of the Micro-Tom (MT) tomato by 24%. The application also modified MT root architecture, with an increase of 26% in the average lateral root length and inhibition of the axial root. At the cellular level, RZ2MS9-treated MT plants presented elongated root cortical cells with intensified mitotic activity. Altogether, these are the best characterized auxin-associated phenotypes. Besides that, no growth alteration was detected in the auxin-insensitive
diageotropic
(
dgt
) plants either with or without the RZ2MS9 inoculation. Our results suggest that auxins play an important role in the ability of
B. thuringiensis
RZ2MS9 to promote MT growth and provide a better understanding of the auxin production mechanism by a
Bt
strain.
SUMMARY
The sugarcane (Saccharum spp.) genome is one of the most complex of all. Modern varieties are highly polyploid and aneuploid as a result of hybridization between Saccharum officinarum and S. ...spontaneum. Little research has been done on meiotic control in polyploid species, with the exception of the wheat Ph1 locus harboring the ZIP4 gene (TaZIP4‐B2) which promotes pairing between homologous chromosomes while suppressing crossover between homeologs. In sugarcane, despite its interspecific origin, bivalent association is favored, and multivalents, if any, are resolved at the end of prophase I. Thus, our aim herein was to investigate the purported genetic control of meiosis in the parental species and in sugarcane itself. We investigated the ZIP4 gene and immunolocalized meiotic proteins, namely synaptonemal complex proteins Zyp1 and Asy1. The sugarcane ZIP4 gene is located on chromosome 2 and expressed more abundantly in flowers, a similar profile to that found for TaZIP4‐B2. ZIP4 expression is higher in S. spontaneum a neoautopolyploid, with lower expression in S. officinarum, a stable octoploid species. The sugarcane Zip4 protein contains a TPR domain, essential for scaffolding. Its 3D structure was also predicted, and it was found to be very similar to that of TaZIP4‐B2, reflecting their functional relatedness. Immunolocalization of the Asy1 and Zyp1 proteins revealed that S. officinarum completes synapsis. However, in S. spontaneum and SP80‐3280 (a modern variety), no nuclei with complete synapsis were observed. Importantly, our results have implications for sugarcane cytogenetics, genetic mapping, and genomics.
Significance Statement
Our work provides insights into the genetic control of meiosis in sugarcane (Saccharum spp.), a man made polyploid and fertile plant of interspecific constitution. Inspired by the discoveries of the Ph1 locus, which harbors the ZIP4 gene in wheat, we identified this meiotic gene in both parental species and in two current sugarcane varieties. We analyzed both gene and protein sequence conservation, protein domains, and predicted the 3D‐protein structure. We also investigated the level of ZIP4 expression in different sugarcane tissues. Like its role in wheat, ZIP4 seems to promote pairing between homologous chromosomes while suppressing crossover between homeologs in Saccharum. Using immunocytology, we were able to determine synaptonemal complex polymerization during prophase I, using Asy1 and Zyp1 sugarcane specific antibodies, revealing synapsis defects in all genotypes except Saccharum officinarum, a parental species with regular meiotic behavior.
The deficiency of calcium (Ca) reduces the quality and shelf life of fruits. In this scenario, although foliar spraying of Ca
has been used, altogether with soil fertilization, as an alternative to ...prevent deficiencies, little is known regarding its absorption dynamics by plant leaves. Herein, in vivo microprobe X-ray fluorescence was employed aiming to monitor the foliar absorption of CaCl
, Ca-citrate complex, and Ca
(PO
)
nanoparticles with and without using adjuvant. We also investigated whether Sr
can be employed as Ca
proxy in foliar absorption studies. Moreover, the impact of treatments on the cuticle structure was evaluated by scanning electron microscopy. For this study, 45-day-old tomato (
L., cv. Micro-Tom) plants were used as a model species. After 100 h, the leaves absorbed 90, 18, and 4% of aqueous CaCl
, Ca-citrate, and Ca
(PO
)
nanoparticles, respectively. The addition of adjuvant increased the absorption of Ca-citrate to 28%, decreased that of CaCl
to 77%, and did not affect Ca
(PO
)
. CaCl
displayed an exponential decay absorption profile with half-lives of 15 h and 5 h without and with adjuvant, respectively. Ca-citrate and Ca
(PO
)
exhibited absorption profiles that were closer to a linear behavior. Sr
was a suitable Ca
tracer because of its similar absorption profiles. Furthermore, the use of adjuvant affected the epicuticular crystal structure. Our findings reveal that CaCl
was the most efficient Ca
source. The effects caused by adjuvant suggest that CaCl
and Ca-citrate were absorbed mostly through hydrophilic and lipophilic pathways.
Austropuccinia psidii is a biotrophic fungus that causes myrtle rust. First described in Brazil, it has since spread to become a globally important pathogen that infects more than 480 myrtaceous ...species. One of the most important commercial crops affected by A. psidii is eucalypt, a widely grown forestry tree. The A. psidii–Eucalyptus spp. interaction is poorly understood, but pathogenesis is likely driven by pathogen-secreted effector molecules. Here, we identified and characterized a total of 255 virulence effector candidates using a genome assembly of A. psidii strain MF-1, which was recovered from Eucalyptus grandis in Brazil. We show that the expression of seven effector candidate genes is modulated by cell wax from leaves sourced from resistant and susceptible hosts. Two effector candidates with different subcellular localization predictions, and with specific gene expression profiles, were transiently expressed with GFP-fusions in Nicotiana benthamiana leaves. Interestingly, we observed the accumulation of an effector candidate, Ap28303, which was upregulated under cell wax from rust susceptible E. grandis and described as a peptidase inhibitor I9 domain-containing protein in the nucleus. This was in accordance with in silico analyses. Few studies have characterized nuclear effectors. Our findings open new perspectives on the study of A. psidii–Eucalyptus interactions by providing a potential entry point to understand how the pathogen manipulates its hosts in modulating physiology, structure, or function with effector proteins.
Histopathology of Phakopsora euvitis on Vitis vinifera Navarro, Barbara Ludwig; Marques, João Paulo Rodrigues; Appezzato-da- Glória, Beatriz ...
European journal of plant pathology,
08/2019, Letnik:
154, Številka:
4
Journal Article
Recenzirano
Rust (
Phakopsora euvitis
) is an important fungal disease in grapevines grown in tropical and subtropical regions. Epidemiological works have been conducted on plant disease resistance, however, ...little is known about defense mechanisms of resistance to the disease. Leaves of
Vitis vinifera
cv. Moscato Giallo were inoculated with
P. euvitis
and lesions were formed with pustules surrounded by water-soaked halo 17 days after inoculation. Foliar tissue of injured and sound material was fixed and submitted to histological techniques. Emergence of pustules from stomata was observed. In water-soaked halo, hyphae of fungus were not observed. In this region, foliar blade presented mesophyll modified by cell hypertrophy with reduction of intercellular spaces and accumulation of pectic compounds. Hypertrophied cells showed parietal thickenings in the cellulose and pectin layers. In the areas delimited by water-soaked halo in the pustule region, the fungus grew vigorously in intercellular spaces of chlorophyll parenchyma; however, vascular bundles also restricted the advance of fungus where sheath cells present parietal pectic thickenings. Therefore, although
Vitis vinifera
cv. Moscato showed rust symptoms on leaves, pathogen colonization was limited by the formation of water-soaked haloes and vascular bundles, which resulted in minor injuries along the foliar limbo.
, the causal agent of myrtle rust, is a biotrophic pathogen whose growth and development depends on the host tissues. The uredospores of
infect
by engaging in close contact with the host surface and ...interacting with the leaf cuticle that provides important chemical and physical signals to trigger the infection process. In this study, the cuticular waxes of
spp. were analyzed to determine their composition or structure and correlation with susceptibility/resistance to
. Twenty-one
spp. in the field were classified as resistant or susceptible. The resistance/susceptibility level of six
spp. were validated in controlled conditions using qPCR, revealing that the pathogen can germinate on the eucalyptus surface of some species without multiplying in the host. CG-TOF-MS analysis detected 26 compounds in the
spp. cuticle and led to the discovery of the role of hexadecanoic acid in the susceptibility of
and
to
. We characterized the epicuticular wax morphology of the six previously selected
spp. using scanning electron microscopy and observed different behavior in
germination during host infection. It was found a correlation of epicuticular morphology on the resistance to
. However, in this study, we provide the first report of considerable interspecific variation in
spp. on the susceptibility to
and its correlation with cuticular waxes chemical compounds that seem to play a synergistic role as a preformed defense mechanism.
Citrus relatives are a relevant source of valuable traits for use in citrus breeding, including resistance to diseases such as Huanglongbing (HLB). Resistant rootstocks may impact tree responses to ...HLB. This requires graft compatibility, which has been poorly investigated within the Aurantioideae. In this study, the biometric characteristics and the anatomy of the graft union of 86 scion/rootstock combinations were assessed. This comprised 18 genotypes/species and 8 genera from Citrinae, Balsamocitrinae, and Clauseninae subtribes sensu Swingle and Reece. Most graft combinations were found to be noncompatible. Phylogenetic proximity did not ensure successful grafting as, for example, Orange jasmine autografts failed, whereas some intergeneric grafts were successful (>60% of graft-take). Plant scion height was directly related to graft-take, but the correlation between the scion and rootstock stem diameters was not a reliable indicator of graft compatibility. Rangpur/Tabog, Tabog/Rangpur, Wampee/Rangpur, Wampee/Pomeroy, Wampee/Swingle, Pomeroy/Wampee, and Swingle/Wampee were the most compatible intergeneric graft combinations. Graft-take success for this was at similar levels to those of sweet orange grafted on common citrus rootstocks. The position as a scion or rootstock in the combination affected the performance and was specific to the genotypes tested. The lack of differentiation between xylem-derived calli and the accumulation of phenolic compounds at the graft union were clear anatomical and biochemical markers, respectively, of incompatibility for most Aurantioideae combinations. In the field, within a set of the ten most promising combinations, Hamlin/Rangpur (control) was the only one that became infected by ‘Candidatus Liberibacter asiaticus’. This was first observed 12 months after planting. Overall, the assessment of biometric traits and anatomy of the graft union allowed Aurantioideae genotypes to be divided into four clusters, with respect to their graft compatibility, as follows: fully compatible with high graft-take and plant growth; potentially compatible with high graft-take but lower plant growth; partially incompatible with lower graft-take and poor plant growth; and fully incompatible with a complete absence of graft-take.
•Multielemental evaluation using a chemometric approach.•Increase in Rh-Lα load values due to water absorption.•Identification of the multielemental spatial distribution using XRF.•Determination of ...correlations in hyperspectral data.
Laboratory microprobe X-ray fluorescence (μ-XRF) spectrometry is a powerful analytical technique able to detect trace elements in biological samples. The present study compared univariate and multivariate strategies to investigate the elements detected with μ-XRF during soybean (Glycine max (L.) Merrill) germination. The conventional approach, i.e., univariate, showed that the studied micronutrients (Mn, Fe, and Zn) were located mainly on the radicle tip, while the macronutrients (P, S, K, and Ca) were spread through the seed. The score maps, as well the correlation maps from a covariance matrix, were able to evaluate variations of chemical elements, such as P, S, K, Ca, Fe, Mn, Zn, and Rh-scattering effects through the embryo, leading the first glance at elemental distribution and remobilization during soybean seed germination.
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