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Chemical nitrogen (N) fertilizer is widely used in sugarcane production, especially in China and India. Understanding the molecular mechanisms and mining miRNAs and their target genes associated with nitrogen use efficiency (NUE) in sugarcane can aid in developing the N-efficient varieties, and thus is beneficial to reduce N fertilizer application. In this study, the root miRNA database of N-efficient sugarcane variety ROC22 under low N stress (0.3 mM NH4NO3) for 3 h was constructed, along with their transcriptome-rearranged data. KEGG analysis indicated that those candidate target genes, corresponding to differentially expressed miRNAs, were mainly enriched in N metabolism, amino acid metabolism, carbohydrate metabolism, photosynthesis, and hormone signal transduction pathways. It was found that under low N stress for 0–24 h, there was a negative correlation between miR168 and SPX, along with miR396 and acnA. Furthermore, the expression of miR156 in the roots of ROC22 was significantly up-regulated under low N treatment. Compared with the wild-type, the Arabidopsis plants overexpressing sugarcane miR156 exhibited significantly improved length and surface area of roots, while the expression of one NO3− transporter gene NRT1.1, three N assimilation key genes (NR1, NIR1, and GS), and the activity of two N assimilation key enzymes (NR and GS) were up-regulated under low N treatment. It can be reasonably deduced that sugarcane miR156 can enhance the nitrogen assimilation ability of the overexpressed Arabidopsis plants under low N application, and thus has a potential ability for improving sugarcane NUE. The present study should be helpful for understanding the molecular regulatory network in the N-efficient sugarcane genotype responding to low N stress and could provide the candidate miRNAs with a potential function in improving sugarcane NUE. [ABSTRACT FROM AUTHOR]

We developed sugarcane plants with improved resistance to the sugarcane borer, Diatraea saccharalis (F). An expression vector pGcry1Ac0229, harboring the cry1Ac gene and the selectable marker gene, bar, was constructed. This construct was introduced into the sugarcane cultivar FN15 by particle bombardment. Transformed plantlets were identified after selection with Phosphinothricin (PPT) and Basta. Plantlets were then screened by PCR based on the presence of cry1Ac and 14 cry1Ac positive plantlets were identified. Real-time quantitative PCR (RT-qPCR) revealed that the copy number of cry1Ac gene in the transgenic lines varied from 1 to 148. ELISA analysis showed that Cry1Ac protein levels in 7 transgenic lines ranged from 0.85 μg/FWg to 70.92 μg/FWg in leaves and 0.04 μg/FWg to 7.22 μg/FWg in stems, and negatively correlated to the rate of insect damage that ranged from 36.67% to 13.33%, respectively. Agronomic traits of six transgenic sugarcane lines with medium copy numbers were similar to the non-transgenic parental line. However, phenotype was poor in lines with high or low copy numbers. Compared to the non-transgenic control plants, all transgenic lines with medium copy numbers had relatively equal or lower sucrose yield and significantly improved sugarcane borer resistance, which lowered susceptibility to damage by insects. This suggests that the transgenic sugarcane lines harboring medium copy numbers of the cry1Ac gene may have significantly higher resistance to sugarcane borer but the sugarcane yield in these lines is similar to the non-transgenic control thus making them superior to the control lines. [ABSTRACT FROM AUTHOR]

Background: Sugarcane (Saccharum spp. hybrids) is considered the most globally important sugar-producing crop and raw material for biofuel. Insect attack is a major issue in sugarcane cultivation, resulting in yield losses and sucrose content reductions. Stem borer (Diatraea saccharalis F.) causes serious yield losses in sugarcane worldwide. However, insect-resistant germplasms for sugarcane are not available in any collections all over the world, and the molecular mechanism of insect resistance has not been elucidated. In this study, cry1Ac transgenic sugarcane lines were obtained and the biological characteristics and transgene dosage effect were investigated and a global exploration of gene expression by transcriptome analysis was performed. Results: The transgene copies of foreign cry1Ac were variable and random. The correlation between the cry1Ac protein and cry1Ac gene copies differed between the transgenic lines from FN15 and ROC22. The medium copy lines from FN15 showed a significant linear relationship, while ROC22 showed no definite dosage effect. The transgenic lines with medium copies of cry1Ac showed an elite phenotype. Transcriptome analysis by RNA sequencing indicated that up/down regulated differentially expressed genes were abundant among the cry1Ac sugarcane lines and the receptor variety. Foreign cry1Ac gene and endogenous borer stress-related genes may have a synergistic effect. Three lines, namely, A1, A5, and A6, were selected for their excellent stem borer resistance and phenotypic traits and are expected to be used directly as cultivars or crossing parents for sugarcane borer resistance breeding. Conclusions: Cry1Ac gene integration dramatically improved sugarcane insect resistance. The elite transgenic offspring contained medium transgene copies. Foreign cry1Ac gene integration and endogenous borer stress-related genes may have a synergistic effect on sugarcane insect resistance improvement. [ABSTRACT FROM AUTHOR]

Abstract Background Sugarcane smut, which is caused by Sporisorium scitamineum , is a severe fungal disease affecting sugarcane. However, the major pathways involved in the interaction between sugarcane and S. scitamineum remains unclear. Results In the present study, suppression subtractive hybridization (SSH) library construction, together with reverse northern blotting, was conducted on the most prevalent sugarcane genotype ROC22 challenged with S. scitamineum. After alignment and homologous expressed sequence tag (EST) assembly, a total of 155 differentially expressed unigenes were identified from SSH libraries. Totally, 26 of 155 differentially expressed unigenes were analyzed by qRT-PCR in sugarcane smut-resistant genotype YC05-179 and susceptible genotype ROC22. Genes encoded two unknown protein (Q1 and Q11), serine/threonine kinase (Q2), fiber protein (Q3), eukaryotic translation initiation factor 5A (Q23), and Sc14-3-3-like protein (Q24) were induced in sugarcane smut-resistant genotype YC05-179 but inhibited in susceptible genotype ROC22. Based on the differential expression data achieved from SSH libraries and qRT-PCR, we found that, serine/threonine kinases, Ca2+ sensors, mitogen-activated protein genes and some NBS-LRR genes may involve in the signal recognition and transduction of smut fungus infection in sugarcane. While in the plant hormone signaling pathways, the genes related to auxin, abscisic acid, salicylic acid and ethylene were more apparently in response to smut fungus invasion. The hypersensitive response, protein metabolism, polyamine synthesis, and cell wall formation may play an important role in sugarcane defense against smut fungus colonization. Additionally, the Sc14-3-3 might serve as a molecular modulator in sugarcane being immune to smut disease by interacting with proteins like ScGAPN (Q10), which have been further verified by BiFC assay. Conclusions The findings of the present study could provide a general view about gene pathways involving in sugarcane defense against smut disease and facilitate a better understanding of the molecular mechanism underlying sugarcane- S. scitamineum interaction. Highlights • Major pathways in response to S. scitamineum challenge of sugarcane were identified in this study. • The 26 differentially expressed unigenes were analyzed both in sugarcane smut-resistant and susceptible genotype. • There is an interaction between Sc14-3-3 and ScGAPN by Pearson correlation analysis and BiFC assay respectively. • The study extends the understanding of sugarcane in response to S. scitamineum infection [ABSTRACT FROM AUTHOR]