Identification of Conserved and Divergent Strigolactone Receptors in Sugarcane Reveals a Key Residue Crucial for Plant Branching Control

Strigolactones (SLs) are a class of important plant hormones mainly regulating plant architecture such as branching, which is crucial for crop yield. It is valuable to study SL signaling pathway and its physiological function in sugarcane, the most important sugar crop, for further molecular breeding. Here, two putative SL receptors SsD14a/b and the interacting F-box protein SsMAX2 were identified in Saccharum spontaneum. SL induced both SsD14a and SsD14b to interact with SsMAX2 in yeast. SsD14a, but not SsD14b, could bind with AtMAX2 and AtSMXL7/SsSMXL7. Overexpression of SsD14a or SsMAX2 rescued the increased branching phenotypes of Arabidopsis thaliana d14-1 or max2-3 mutants, respectively. Moreover, the crystal structure of N-terminal truncated SsD14a was solved, with an overall structure identical to AtD14 and OsD14 in the open state, consistent with its conserved branching suppression capacity in Arabidopsis. In line with the biochemical observations, SsD14b could not completely complement in d14-1 although these two SsD14 proteins have almost identical primary sequences except for very few residues. Complement with the combination of SsD14b and SsMAX2 still failed to rescue the d14-1 max2-3 double mutant multi-branching phenotype, indicating SsD14b–AtSMXL7 complex formation is required for regulating branching. Mutagenesis analyses revealed that residue R310 at α10 helix of SsD14a was crucial for the binding with SsSMXL7/AtSMXL7 but not SsMAX2. The site-equivalent single-residue P304R substitution enabled SsD14b to bind with AtMAX2 and AtSMXL7/SsSMXL7 and to rescue the phenotype of d14-1 max2-3 together with SsMAX2. Moreover, this conserved Arg residue across species including rice and Arabidopsis determined the activity of SL receptors through maintaining their interaction with SMXL repressors. Taken together, our work identified conserved and divergent strigolactone receptors in sugarcane core SL signaling pathway and revealed a key residue crucial for plant branching control.

Analysis of metal accumulation and Phytochelatin Synthase (PCS) gene expression in Saccharum spontaneum L. as regards its function for remediation of lead (Pb) contamination

Pollution caused by heavy metals, has become a serious problem. Adverse effects arising from the increased use of heavy metals in a variety of human activities lead to any environmental degradation. Lead (Pb) is one of most common contaminants in the environment and highly toxic. Pb is less mobile, so its compound tends to accumulate in soil and sediments. Definitely, efforts are needed to remove this contaminant in the environment. Saccharum spontaneum L. is a perennial grass which has potential to be used as an accumulator plant to clean up pollutants. The ability of this plant as metal accumulator was tested in this study. S.pontaneum plants were treated using Pb in the concentrations of 0 ppm (control), 100 ppm, 200 ppm, and 300 ppm for 8 weeks. The results showed that there was an increase in the percentage of relative accumulation of Pb in the treated plants. This also indicated that plant roots accumulated more Pb than shoots. Meanwhile, expression of Phytochelatin synthase (PCS) gene increased 1.3-to-3.5-fold inductions in roots by increasing concentration of Pb treatments for 24 h. PCS gene expression showed the higher induction in the roots than in the shoots of S.spontaneum plant under Pb treatments.

Chromosome Painting Provides Insights Into the Genome Structure and Evolution of Sugarcane

The genus Saccharum is composed of species with high polyploidy and highly varied chromosome numbers, laying a challenge for uncovering its genomic structure and evolution. We developed a chromosome 2 painting (CP2) probe by designing oligonucleotides covering chromosome 2 of Saccharum spontaneum (2n = 8x = 64). Fluorescence in situ hybridization (FISH) using this CP2 probe revealed six types of ploidies from twenty S. spontaneum clones, including 6x, 8x, 10x, 11x, 12x, and 13x clones. The finding of S. spontaneum clones with uneven of ploid suggested that certain S. spontaneum clones come from hybridization. It renews our knowledge that S. spontaneum is derived from autopolyploidization. Combined with a S. spontaneum-specific probe, chromosome 2-derived chromosome or fragments from either S. spontaneum or Saccharum officinarum can be identified in sugarcane modern cultivars. We revealed unexpected high level of interspecific recombination from introgressive S. spontaneum chromosomes (>50.0%) in cultivars ROC22 and ZZ1, indicating frequent chromosome exchange in cultivars. Intriguingly, we observed interspecific recombination recurring among either homoeologous or non-homoeologous chromosomes in sugarcane cultivars. These results demonstrated that chromosome painting FISH is a powerful tool in the genome dissection of sugarcane and provide new insights into the genome structure and evolution of the complex genus Saccharum.

Silicon via nutrient solution modulates deficient and sufficient manganese sugar and energy cane antioxidant systems

Manganese (Mn) is highly demanded by Poaceae, and its deficiency induces physiological and biochemical responses in plants. Silicon (Si), which is beneficial to plants under various stress conditions, may also play an important role in plants without stress. However, the physiological and nutritional mechanisms of Si to improve Mn nutrition in sugarcane and energy cane, in addition to mitigating deficiency stress, are still unclear. The objective of this study is to evaluate whether the mechanisms of action of Si are related to the nutrition of Mn by modulating the antioxidant defense system of sugarcane plants and energy cane plants cultivated in nutrient solution, favoring the physiological and growth factors of plants cultivated under Mn deficiency or sufficiency. Two experiments were carried out with pre-sprouted seedlings of Saccharum officinarum L. and Saccharum spontaneum L. grown in the nutrient solution. Treatments were arranged in a 2 × 2 factorial design. Plants were grown under Mn sufficiency (20.5 µmol L−1) and the deficiency (0.1 µmol L−1) associated with the absence and presence of Si (2.0 mmol L−1). Mn deficiency caused oxidative stress by increasing lipid peroxidation and decreasing GPOX activity, contents of phenols, pigments, and photosynthetic efficiency, and led to the growth of both studied species. Si improved the response of both species to Mn supply. The attenuation of the effects of Mn deficiency by Si depends on species, with a higher benefit for Saccharum spontaneum. Its performance is involved in reducing the degradation of cells by reactive oxygen species (21%), increasing the contents of phenols (18%), carotenoids (64%), proteins, modulating SOD activity, and improving photosynthetic and growth responses.

Genome-wide analysis of R2R3-MYB transcription factors family in the autopolyploid Saccharum spontaneum: an exploration of dominance expression and stress response

Background Sugarcane (Saccharum) is the most critical sugar crop worldwide. As one of the most enriched transcription factor families in plants, MYB genes display a great potential to contribute to sugarcane improvement by trait modification. We have identified the sugarcane MYB gene family at a whole-genome level through systematic evolution analyses and expression profiling. R2R3-MYB is a large subfamily involved in many plant-specific processes. Results A total of 202 R2R3-MYB genes (356 alleles) were identified in the polyploid Saccharum spontaneum genomic sequence and classified into 15 subgroups by phylogenetic analysis. The sugarcane MYB family had more members by a comparative analysis in sorghum and significant advantages among most plants, especially grasses. Collinearity analysis revealed that 70% of the SsR2R3-MYB genes had experienced duplication events, logically suggesting the contributors to the MYB gene family expansion. Functional characterization was performed to identify 56 SsR2R3-MYB genes involved in various plant bioprocesses with expression profiling analysis on 60 RNA-seq databases. We identified 22 MYB genes specifically expressed in the stem, of which RT-qPCR validated MYB43, MYB53, MYB65, MYB78, and MYB99. Allelic expression dominance analysis implied the differential expression of alleles might be responsible for the high expression of MYB in the stem. MYB169, MYB181, MYB192 were identified as candidate C4 photosynthetic regulators by C4 expression pattern and robust circadian oscillations. Furthermore, stress expression analysis showed that MYB36, MYB48, MYB54, MYB61 actively responded to drought treatment; 19 and 10 MYB genes were involved in response to the sugarcane pokkah boeng and mosaic disease, respectively. Conclusions This is the first report on genome-wide analysis of the MYB gene family in sugarcane. SsMYBs probably played an essential role in stem development and the adaptation of various stress conditions. The results will provide detailed insights and rich resources to understand the functional diversity of MYB transcription factors and facilitate the breeding of essential traits in sugarcane.

The Wild Sugarcane and Sorghum Kinomes: Insights Into Expansion, Diversification, and Expression Patterns

The protein kinase (PK) superfamily is one of the largest superfamilies in plants and the core regulator of cellular signaling. Despite this substantial importance, the kinomes of sugarcane and sorghum have not been profiled. Here, we identified and profiled the complete kinomes of the polyploid Saccharum spontaneum (Ssp) and Sorghum bicolor (Sbi), a close diploid relative. The Sbi kinome was composed of 1,210 PKs; for Ssp, we identified 2,919 PKs when disregarding duplications and allelic copies, and these were related to 1,345 representative gene models. The Ssp and Sbi PKs were grouped into 20 groups and 120 subfamilies and exhibited high compositional similarities and evolutionary divergences. By utilizing the collinearity between the species, this study offers insights into Sbi and Ssp speciation, PK differentiation and selection. We assessed the PK subfamily expression profiles via RNA-Seq and identified significant similarities between Sbi and Ssp. Moreover, coexpression networks allowed inference of a core structure of kinase interactions with specific key elements. This study provides the first categorization of the allelic specificity of a kinome and offers a wide reservoir of molecular and genetic information, thereby enhancing the understanding of Sbi and Ssp PK evolutionary history.

SACCHARUM SPONTANEUM L. EVALUADA COMO SUSTRATO SÓLIDO ORGÁNICO NATURAL EN DESNITRIFICACIÓN BIOLÓGICA

Aproximadamente el 12% del suelo de la República de Panamá es usado para actividades ganaderas agrícolas e industriales, esto ha causado alteraciones en el Ciclo de Nitrógeno presentando aumentos en los niveles de Nitrato presentes en las aguas subterráneas, residuales y superficiales. En el año 2000 las concentraciones de Nitrato sobrepasan los 50mg/L [9] en un 20% y 60%; este desequilibrio es causante de graves afecciones a la salud, además de los daños al ecosistema acuático. Una alternativa eficiente para la remoción de este compuesto son los Sustratos Sólidos Orgánicos Naturales (SSON) como fuente de carbono orgánico para el proceso de desnitrificación. Nuestro estudio utiliza la Paja Canalera (Saccharum Spontaneum L.) como SSON para reducir las concentraciones de nitrato presente en el agua. La cosecha se dio en la Universidad Tecnológica de Panamá, se realizaron ensayos bromatológicos, pruebas de lixiviación para determinar la sección optima de la planta para el aprovechamiento del carbono soluble. Además, realizamos pruebas Batch para determinar el aporte total de carbón soluble y la tasa de liberación. Los resultados fueron alentadores con 99.85% de remoción de Nitrato con tasa de liberación de 0.12 d-1 y el aporte final de 711 mg de DQO. La eliminación del Nitrato es evidente hasta el agotamiento del aporte de carbono por la Saccharum s., esto demuestra el potencial de la planta para este proceso. Se requiere profundizar en más estudios para establecer sus usos, ya que, representan una alternativa factible por su bajo costo y fácil acceso.

PENGARUH PEMBERIAN INFUSA BATANG GELAGAH (Saccharum spontaneum L.) TERHADAP KADAR GLUKOSA DARAH MENCIT PUTIH (Mus musculus L.) JANTAN YANG DIINDUKSI GLUKOSA

Telah dilakukan penelitian tentang pengaruh infusa batang gelagah (Saccharum spontaneum L.) terhadap kadar glukosa darah mencit putih (Mus musculus L.) jantan yang diinduksi glukosa. Penelitian ini bertujuan untuk melihat pengaruh infusa batang gelagah (Saccharum spontaneum L.) terhadap kadar glukosa darah mencit putih (Mus musculus L.) jantan yang diinduksi glukosa 2g/KgBB. Penelitian ini menggunakan metode Tes Toleransi Glukosa Oral (TTGO). Hewan percobaan dibagi menjadi 6 kelompok. Kelompok kontrol negatif hanya diberikan akuades, kelompok kontrol pembanding hanya diberikan larutan glukosa 2g/KgBB, kelompok positif diberi Metfromin dengan dosis 65mg/KgBB, kelompok perlakuan diberi sediaan infusa batang gelagah (Saccharum spontaneum L.) dengan konsentrasi 10%, 20% dan 30%. Setelah masing-masing hewan uji diberi perlakuan 30 menit kemudian diberi glukosa 2g/KgBB secara oral. Kemudian dilakukan pengukuran kadar glukosa darah mencit pada menit 30-180. Berdasarkan hasil pengujian infusa batang gelagah (Saccharum spontaneum L.) menunjukkan bahwa konsentrasi 10%, 20% dan 30% memiliki penurunan kadar glukosa darah mencit putih (Mus musculus L). Hasil yang diperoleh dari hasil uji ANOVA dua arah dilanjutkan dengan uji Post Hoc Tukey juga menunjukkan bahwa lama pemberian dapat mempengaruhi penurunan kadar glukosa darah mencit (p<0,05).

Genome-wide identification and expression profiling of DREB genes in Saccharum spontaneum

Background The dehydration-responsive element-binding proteins (DREBs) are important transcription factors that interact with a DRE/CRT (C-repeat) sequence and involve in response to multiple abiotic stresses in plants. Modern sugarcane are hybrids from the cross between Saccharum spontaneum and Saccharum officinarum, and the high sugar content is considered to the attribution of S. officinaurm, while the stress tolerance is attributed to S. spontaneum. To understand the molecular and evolutionary characterization and gene functions of the DREBs in sugarcane, based on the recent availability of the whole genome information, the present study performed a genome-wide in silico analysis of DREB genes and transcriptome analysis in the polyploidy S. spontaneum. Results Twelve DREB1 genes and six DREB2 genes were identified in S. spontaneum genome and all proteins contained a conserved AP2/ERF domain. Eleven SsDREB1 allele genes were assumed to be originated from tandem duplications, and two of them may be derived after the split of S. spontaneum and the proximal diploid species sorghum, suggesting tandem duplication contributed to the expansion of DREB1-type genes in sugarcane. Phylogenetic analysis revealed that one DREB2 gene was lost during the evolution of sugarcane. Expression profiling showed different SsDREB genes with variable expression levels in the different tissues, indicating seven SsDREB genes were likely involved in the development and photosynthesis of S. spontaneum. Furthermore, SsDREB1F, SsDREB1L, SsDREB2D, and SsDREB2F were up-regulated under drought and cold condition, suggesting that these four genes may be involved in both dehydration and cold response in sugarcane. Conclusions These findings demonstrated the important role of DREBs not only in the stress response, but also in the development and photosynthesis of S. spontaneum.