Plant microbiome and its manipulation inaugurate a new era for plant biotechnology with the potential to benefit sustainable crop production. Here, we used the large-scale 16S rDNA sequencing ...analysis to unravel the dynamic, structure, and composition of exophytic and endophytic microbial communities in two hybrid commercial cultivars of sugarcane (R570 and SP80-3280), two cultivated genotypes (Saccharum officinarum and Saccharum barberi) and one wild species (Saccharum spontaneum). Our analysis identified 1372 amplicon sequence variants (ASVs). The microbial communities' profiles are grouped by two, root and bulk soils and stem and leave when these four components are compared. However, PCoA-based data supports that endophytes and epiphytes communities form distinct groups, revealing an active host-derived mechanism to select the resident microbiota. A strong genotype-influence on the assembly of microbial communities in Saccharum ssp. is documented. A total of 220 ASVs persisted across plant cultivars and species. The ubiquitous bacteria are two potential beneficial bacteria, Acinetobacter ssp., and Serratia symbiotica. The results presented support the existence of common and cultivar-specific ASVs in two commercial hybrids, two cultivated canes and one species of Saccharum across tissues (leaves, stems, and roots). Also, evidence is provided that under the experimental conditions described here, each genotype bears its microbial community with little impact from the soil conditions, except in the root system. It remains to be demonstrated which aspect, genotype, environment or both, has the most significant impact on the microbial selection in sugarcane fields.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Sugarcane is an important agricultural crop in the economy of tropical regions, and Brazil has the largest cultivated acreage in the world. Sugarcane accumulates high levels of sucrose in its stalks. ...Other compounds produced by sugarcane are currently not of economic importance. To explore potential coproducts, we have studied the chemical diversity of sugarcane genotypes, via metabolite profiling of leaves by NMR and LC-DAD-MS. Metabolites were identified via in-house and public databases. From the analysis of 60 HPLC-fractionated extracts, LC-DAD-MS detected 144 metabolites, of which 56 were identified (MS-MS and 1H NMR), including 19 phenolics and 25 flavones, with a predominance of isomeric flavone C-glycosides. Multivariate analysis of the profiles from genotypes utilized in Brazilian breeding programs revealed clustering according to sugar, phenolic acid, and flavone contents.
Sporisorium scitamineum is the causal agent of sugarcane smut disease. In this study, we characterized sugarcane reactive oxygen species (ROS) metabolism in response to the pathogen in smut-resistant ...and-susceptible genotypes. Sporisorium scitamineum teliospore germination and appressorium formation coincided with H₂O₂ accumulation in resistant plants. The superoxide dismutase (SOD) activity was not responsive in any of the genotypes; however, a higher number of isoenzymes were detected in resistant plants. In addition, related to resistance were lipid peroxidation, a decrease in catalase (CAT), and an increase in glutathione S-transferase (GST) activities and an earlier transcript accumulation ofROS marker genes (CAT3, CATA, CATB, GST31, GSTt3, and peroxidase 5-like). Furthermore, based on proteomic data, we suggested that the source of the increased hydrogen peroxide (H₂O₂) may be due to a protein of the class III peroxidase, which was inhibited in the susceptible genotype. H₂O₂ is sensed and probably transduced through overlapping systems related to ascorbate–glutathione and thioredoxin to influence signalling pathways, as revealed by the presence of thioredoxin h-type, ascorbate peroxidase, and guanine nucleotide-binding proteins in the infected resistant plants. Altogether, our data depicted the balance of the oxidative burst and antioxidant enzyme activity in the outcome of this interaction.
The role of bundle sheath conductance (
g
bs
) in sustaining sugarcane photosynthesis under nitrogen deficiency was investigated. Sugarcane was grown under different levels of nitrogen supply and
g
...bs
was estimated using simultaneous measurements of leaf gas exchange and chlorophyll fluorescence at 21% or 2% O
2
and varying air CO
2
and light intensity. Maximum rates of PEPC carboxylation, Rubisco carboxylation, and ATP production increased with an increase in leaf nitrogen concentration (LNC) from 1 to 3 g m
−2
. Low nitrogen supply reduced Rubisco and PEPC abundancies, the quantum efficiency of CO
2
assimilation and
g
bs
. Because of reduced
g
bs
, low photosynthetic rates were not associated with increased leakiness under nitrogen deficiency. In fact, low nitrogen supply increased bundle sheath cell wall thickness, probably accounting for low
g
bs
and increased estimates of CO
2
at Rubisco sites. Effects of nitrogen on expression of
Sh
PIP2;1
and
Sh
PIP1;2
aquaporins did not explain changes in
g
bs
. Our data revealed that reduced Rubisco carboxylation was the main factor causing low sugarcane photosynthesis at low nitrogen supply, in contrast to the previous report on the importance of an impaired CO
2
concentration mechanism under N deficiency. Our findings suggest higher investment of nitrogen into Rubisco protein would favour photosynthesis and plant performance under low nitrogen availability.
Sugarcane is an important crop worldwide for sugar and first generation ethanol production. Recently, the residue of sugarcane mills, named bagasse, has been considered a promising lignocellulosic ...biomass to produce the second-generation ethanol. Lignin is a major factor limiting the use of bagasse and other plant lignocellulosic materials to produce second-generation ethanol. Lignin biosynthesis pathway is a complex network and changes in the expression of genes of this pathway have in general led to diverse and undesirable impacts on plant structure and physiology. Despite its economic importance, sugarcane genome was still not sequenced. In this study a high-throughput transcriptome evaluation of two sugarcane genotypes contrasting for lignin content was carried out. We generated a set of 85,151 transcripts of sugarcane using RNA-seq and de novo assembling. More than 2,000 transcripts showed differential expression between the genotypes, including several genes involved in the lignin biosynthetic pathway. This information can give valuable knowledge on the lignin biosynthesis and its interactions with other metabolic pathways in the complex sugarcane genome.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Saccharum spontaneum
,
S. robustum
and
S. officinarum
are the founding polyploid genomes of the modern varieties of sugarcane (
Saccharum
spp.). The crop is one of the world's major sugar and ...biomass-producing crops, potential sources of renewable energy. Understanding the genomic relationships among the founding genomes is crucial if we are to develop disease/drought-resistant varieties to counter the threat posed by climate change.
Saccharum
cytogenetics is a growing field, and significant progress has been achieved particularly in
S. spontaneum
(
x
= 8,
2n
= 5 – 16
x
= 40 – 128, commonly
2n
=
8x
= 64) and
S. officinarum
(
x
= 10,
2n
=
8x
= 80). However, only a few studies on
S. robustum
(
x
= 10,
2n
= 6 −
20x
= 60 − 200) have been conducted, which is thought to be the wild ancestor of
S. officinarum
, a legitimate species, commonly known as noble cane. Herein, using fluorescent in situ hybridization with centromeric probes we found clear evidence that
S. robustum
meiosis is regular (
2n
= 100), exhibiting 50 bivalents, with no univalents or multivalent associations. In addition, using genomic in situ hybridization, we found a close relationship between
S. robustum
and
S. officinarum
and divergence from
S. spontaneum
.
Resistance genes composing the two-layer immune system of plants are thought as important markers for breeding pathogen-resistant crops. Many have been the attempts to establish relationships between ...the genomic content of Resistance Gene Analogs (RGAs) of modern sugarcane cultivars to its degrees of resistance to diseases such as smut. However, due to the highly polyploid and heterozygous nature of sugarcane genome, large scale RGA predictions is challenging.
We predicted, searched for orthologs, and investigated the genomic features of RGAs within a recently released sugarcane elite cultivar genome, alongside the genomes of sorghum, one sugarcane ancestor (Saccharum spontaneum), and a collection of de novo transcripts generated for six modern cultivars. In addition, transcriptomes from two sugarcane genotypes were obtained to investigate the roles of RGAs differentially expressed (RGADE) in their distinct degrees of resistance to smut. Sugarcane references lack RGAs from the TNL class (Toll-Interleukin receptor (TIR) domain associated to nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains) and harbor elevated content of membrane-associated RGAs. Up to 39% of RGAs were organized in clusters, and 40% of those clusters shared synteny. Basically, 79% of predicted NBS-encoding genes are located in a few chromosomes. S. spontaneum chromosome 5 harbors most RGADE orthologs responsive to smut in modern sugarcane. Resistant sugarcane had an increased number of RGAs differentially expressed from both classes of RLK (receptor-like kinase) and RLP (receptor-like protein) as compared to the smut-susceptible. Tandem duplications have largely contributed to the expansion of both RGA clusters and the predicted clades of RGADEs.
Most of smut-responsive RGAs in modern sugarcane were potentially originated in chromosome 5 of the ancestral S. spontaneum genotype. Smut resistant and susceptible genotypes of sugarcane have a distinct pattern of RGADE. TM-LRR (transmembrane domains followed by LRR) family was the most responsive to the early moment of pathogen infection in the resistant genotype, suggesting the relevance of an innate immune system. This work can help to outline strategies for further understanding of allele and paralog expression of RGAs in sugarcane, and the results should help to develop a more applied procedure for the selection of resistant plants in sugarcane.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Few studies have evaluated endophytic bacteria in relation to plant growth promotion, nitrogen uptake and biological control. The aim of this study was to molecularly and physiologically characterize ...thirteen endophytic bacteria strains, evaluate their biological control properties and their ability to promote plant growth and plant N nutrition. All the strains produced indole acetic acid and promoted increase of plant biomass, N accumulative amount and N-use efficiency index. None of the strains carries the
nif
H gene. Four strains stimulated plant nitrate reductase activity, four solubilized phosphate, nine produced siderophores and none produced HCN. Seven strains inhibited
Bipolaris sacchari
growth and one was antagonistic to
Ceratocystis paradoxa
. The pathogens were inhibited by the production of diffusible and volatile metabolites by the bacterial strains. Moreover, this is the first study to demonstrate the effect of
Delftia acidovorans
on sugarcane plant growth, nitrogen metabolism improvement and antagonism to
B. sacchari
. The most efficient strains in promoting plant growth and exhibiting antagonistic activities towards fungal pathogens were
Herbaspirillum frinsingense
(IAC-BECa-152) and three
Pantoea dispersa
strains (IAC-BECa-128, IAC-BECa-129, and IAC-BECa-132). These bacteria show potential to be used as inoculants for sustainable agricultural management, mainly at the seedling production phase.
Drought is the most detrimental abiotic stress to sugarcane production. Nevertheless, transcriptomic analyses remain scarce for field-grown plants. Here we performed comparative transcriptional ...profiling of two contrasting sugarcane genotypes, 'IACSP97-7065' (drought-sensitive) and 'IACSP94-2094' (drought-tolerant) grown in a drought-prone environment. Physiological parameters and expression profiles were analyzed at 42 (May) and 117 (August) days after the last rainfall. The first sampling was done under mild drought (soil water potential of -60 kPa), while the second one was under severe drought (soil water potential of -75 kPa). Microarray analysis revealed a total of 622 differentially expressed genes in both sugarcane genotypes under mild and severe drought stress, uncovering about 250 exclusive transcripts to 'IACSP94-2094' involved in oxidoreductase activity, transcriptional regulation, metabolism of amino acids, and translation. Interestingly, the enhanced antioxidant system of 'IACSP94-2094' may protect photosystem II from oxidative damage, which partially ensures stable photochemical activity even after 117 days of water shortage. Moreover, the tolerant genotype shows a more extensive set of responsive transcription factors, promoting the fine-tuning of drought-related molecular pathways. These results help elucidate the intrinsic molecular mechanisms of a drought-tolerant sugarcane genotype to cope with ever-changing environments, including prolonged water deficit, and may be useful for plant breeding programs.
Sugarcane smut disease is caused by the biotrophic fungus Sporisorium scitamineum. The disease is characterized by the development of a whip-like structure from the primary meristems, where billions ...of teliospores are produced. Sugarcane smut also causes tillering and low sucrose and high fiber contents, reducing cane productivity. We investigated the biological events contributing to disease symptoms in a smut intermediate-resistant sugarcane genotype by examining the transcriptional profiles (RNAseq) shortly after inoculating the plants and immediately after whip emission. The overall picture of disease progression suggests that premature transcriptional reprogramming of the shoot meristem functions continues until the emergence of the whip. The guidance of this altered pattern is potentially primarily related to auxin mobilization in addition to the involvement of other hormonal imbalances. The consequences associated with whip emission are the modulation of typical meristematic functions toward reproductive organ differentiation, requiring strong changes in carbon partitioning and energy production. These changes include the overexpression of genes coding for invertases and trehalose-6P synthase, as well as other enzymes from key metabolic pathways, such as from lignin biosynthesis. This is the first report describing changes in the transcriptional profiles following whip development, providing a hypothetical model and candidate genes to further study sugarcane smut disease progression.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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