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BackgroundInternode elongation is one of the most important traits in sugarcane because of its relation to crop productivity. Understanding the microRNA (miRNA) and mRNA expression profiles related to sugarcane internode elongation would help develop molecular improvement strategies but they are not yet well-investigated. To identify genes and miRNAs involved in internode elongation, the cDNA and small RNA libraries from the pre-elongation stage (EI), early elongation stage (EII) and rapid elongation stage (EIII) were sequenced and their expression were studied.ResultsBased on the sequencing results, 499,495,518 reads and 80,745 unigenes were identified from stem internodes of sugarcane. The comparisons of EI vs. EII, EI vs. EIII, and EII vs. EIII identified 493, 5035 and 3041 differentially expressed genes, respectively. Further analysis revealed that the differentially expressed genes were enriched in the GO terms oxidoreductase activity and tetrapyrrole binding. KEGG pathway annotation showed significant enrichment in “zeatin biosynthesis”, “nitrogen metabolism” and “plant hormone signal transduction”, which might be participating in internode elongation. miRNA identification showed 241 known miRNAs and 245 novel candidate miRNAs. By pairwise comparison, 11, 42 and 26 differentially expressed miRNAs were identified from EI and EII, EI and EIII, and EII and EIII comparisons, respectively. The target prediction revealed that the genes involved in “zeatin biosynthesis”, “nitrogen metabolism” and “plant hormone signal transduction” pathways are targets of the miRNAs. We found that the known miRNAs miR2592-y, miR1520-x, miR390-x, miR5658-x, miR6169-x and miR8154-x were likely regulators of genes with internode elongation in sugarcane.ConclusionsThe results of this study provided a global view of mRNA and miRNA regulation during sugarcane internode elongation. A genetic network of miRNA-mRNA was identified with miRNA-mediated gene expression as a mechanism in sugarcane internode elongation. Such evidence will be valuable for further investigations of the molecular regulatory mechanisms underpinning sugarcane growth and development.

Background Although extensive breeding efforts are ongoing in sugarcane (Saccharum officinarum L.), the average yield is far below the theoretical potential. Tillering is an important component of sugarcane yield, however, the molecular mechanism underlying tiller development is still elusive. The limited genomic data in sugarcane, particularly due to its complex and large genome, has hindered in-depth molecular studies. Results Herein, we generated full-length (FL) transcriptome from developing leaf and tiller bud samples based on PacBio Iso-Seq. In addition, we performed RNA-seq from tiller bud samples at three developmental stages (T0, T1 and T2) to uncover key genes and biological pathways involved in sugarcane tiller development. In total, 30,360 and 20,088 high-quality non-redundant isoforms were identified in leaf and tiller bud samples, respectively, representing 41,109 unique isoforms in sugarcane. Likewise, we identified 1063 and 1037 alternative splicing events identified in leaf and tiller bud samples, respectively. We predicted the presence of coding sequence for 40,343 isoforms, 98% of which was successfully annotated. Comparison with previous FL transcriptomes in sugarcane revealed 2963 unreported isoforms. In addition, we characterized 14,946 SSRs from 11,700 transcripts and 310 lncRNAs. By integrating RNA-seq with the FL transcriptome, 468 and 57 differentially expressed genes (DEG) were identified in T1vsT0 and T2vsT0, respectively. Strong up-regulation of several pyruvate phosphate dikinase and phosphoenolpyruvate carboxylase genes suggests enhanced carbon fixation and protein synthesis to facilitate tiller growth. Similarly, up-regulation of linoleate 9S-lipoxygenase and lipoxygenase genes in the linoleic acid metabolism pathway suggests high synthesis of key oxylipins involved in tiller growth and development. Conclusions Collectively, we have enriched the genomic data available in sugarcane and provided candidate genes for manipulating tiller formation and development, towards productivity enhancement in sugarcane.

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The Jinsha River Basin (JRB) is the largest hydropower base in China, serving as the main source of the Western Route of China’s South-to-North Water Diversion Project. Under the influence of the reservoirs operation and climate change, the general hydrological regime in the JRB has been altered. Although the change process can be determined through a runoff time-series analysis and hydrological simulation, the individual impacts of the reservoirs have not been quantified. This study aimed to clarify the impact of the reservoirs in the JRB on the runoff, flood, and drought processes using a framework coupling long short-term memory (LSTM) and flood drought assessment techniques. The results are as follows: (1) From 1998 to 2020, reservoirs in the JRB changed the average daily runoff at Pingshan Station by −5.64%, +10.95%, and −10.93% at the annual and seasonal (dry and rainy) scales, respectively. (2) The operation of dams reduces the risk of flood disasters effectively. Compared with the natural river flow, the flood frequency decreased by 7.69%, and the total flow over the threshold was reduced by 37.86%. (3) The operation of dams has changed the duration and severity of drought, reducing extreme drought and increasing moderate and severe drought. In conclusion, the reservoirs in the JRB have positive effects on water resource regulation, and their mitigation of floods and extreme drought provides security for the middle and lower reaches of the Yangtze River. This study provides a reference for the LSTM modeling of reservoir basins, quantifying the impact of reservoirs on runoff, flood, and drought in the JRB.

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