Sugarcane is the source of sugar in all tropical and subtropical countries and is becoming increasingly important for bio-based fuels. However, its large (10 Gb), polyploid, complex genome has hindered genome based breeding efforts. Here we release the largest and most diverse set of sugarcane genome sequences to date, as part of an on-going initiative to provide a sugarcane genomic information resource, with the ultimate goal of producing a gold standard genome. Three hundred and seventeen chiefly euchromatic BACs were sequenced. A reference set of one thousand four hundred manually-annotated protein-coding genes was generated. A small RNA collection and a RNA-seq library were used to explore expression patterns and the sRNA landscape. In the sucrose and starch metabolism pathway, 16 non-redundant enzyme-encoding genes were identified. One of the sucrose pathway genes, sucrose-6-phosphate phosphohydrolase, is duplicated in sugarcane and sorghum, but not in rice and maize. A diversity analysis of the s6pp duplication region revealed haplotype-structured sequence composition. Examination of hom(e)ologous loci indicate both sequence structural and sRNA landscape variation. A synteny analysis shows that the sugarcane genome has expanded relative to the sorghum genome, largely due to the presence of transposable elements and uncharacterized intergenic and intronic sequences. This release of sugarcane genomic sequences will advance our understanding of sugarcane genetics and contribute to the development of molecular tools for breeding purposes and gene discovery.

Drought severely impacts plant development and reproduction, reducing biomass and seed number, and altering flowering patterns. Drought-tolerant Setaria italica and Setaria viridis species have emerged as prominent model species for investigating water deficit responses in the Poaceae family, the most important source of food and biofuel biomass worldwide. In higher plants, abscisic acid (ABA) regulates environmental stress responses, and its signaling entails interactions between PYR/PYL/RCAR receptors and clade A PP2C phosphatases, which in turn modulate SnRK2 kinases via reversible phosphorylation to activate ABA-responsive genes. To compare the diversity of PYR/PYL/RCAR, PP2C, and SnRK2 between S. italica and S. viridis, and their involvement in water deficit responses, we examined gene and regulatory region structures, investigated orthology relationships, and analyzed their gene expression patterns under water stress via a meta-analysis approach. Results showed that coding and regulatory sequences of PYR/PYL/RCARs, PP2Cs, and SnRK2s are highly conserved between Setaria spp., allowing us to propose pairs of orthologous genes for all the loci identified. Phylogenetic relationships indicate which clades of Setaria spp. sequences are homologous to the functionally well-characterized Arabidopsis thaliana PYR/PYL/RCAR, PP2C, and SnRK2 genes. Gene expression analysis showed a general downregulation of PYL genes, contrasting with upregulation of PP2C genes, and variable expression modulation of SnRK2 genes under drought stress. This complex network implies that ABA core signaling is a diverse and multifaceted process. Through our analysis, we identified promising candidate genes for further functional characterization, with great potential as targets for drought resistance studies, ultimately leading to advances in Poaceae biology and crop-breeding strategies.

Long terminal repeat retrotransposons (LTR-RTs) in plant genomes differ in abundance, structure and genomic distribution, reflecting the large number of evolutionary lineages. Elements within lineages can be considered populations, in which each element is an individual in its genomic environment. In this way, it would be reasonable to apply microevolutionary analyses to understand transposable element (TE) evolution, such as those used to study the genetic structure of natural populations. Here, we applied a Bayesian method to infer genetic structure of populations together with classical phylogenetic and dating tools to analyze LTR-RT evolution using the monocot Setaria italica as a model species. In contrast to a phylogeny, the Bayesian clusterization method identifies populations by assigning individuals to one or more clusters according to the most probabilistic scenario of admixture, based on genetic diversity patterns. In this work, each LTR-RT insertion was considered to be one individual and each LTR-RT lineage was considered to be a single species. Nine evolutionary lineages of LTR-RTs were identified in the S. italica genome that had different genetic structures with variable numbers of clusters and levels of admixture. Comprehensive analysis of the phylogenetic, clusterization and time of insertion data allowed us to hypothesize that admixed elements represent sequences that harbor ancestral polymorphic sequence signatures. In conclusion, application of microevolutionary concepts in genome evolution studies is suitable as a complementary approach to phylogenetic analyses to address the evolutionary history and functional features of TEs.

Full-length Del elements from ten angiosperm genomes, 5 monocot and 5 dicot, were retrieved and putative attachment (att) sites were identified. In the 2432 Del elements, two types of U5 att sites and a single conserved type of U3 att site were identified. Retroviral att sites confer specificity to the integration process, different att sites types therefore implies lineage specificity. While some features are common to all Del elements, CpG island patterns within the LTRs were particular to lineage specific clusters. All eudicot copies grouped into one single clade while the monocots harbour a more diverse collection of elements. Furthermore, full-length Del elements and truncated copies were unevenly distributed amongst chromosomes. Elements of Del lineage are organized in plants into three clusters and each cluster is composed of elements with distinct LTR features. Our results suggest that the Del lineage efficiently amplified in the monocots and that one branch is probably a newly emerging sub-lineage. Finally, sequences in all groups are under purifying selection. These results show the LTR region is dynamic and important in the evolution of LTR-retrotransposons, we speculate that it is a trigger for retrotransposon diversification.

Disinfection and callus induction in forest species is essential to improve genetic production. Although multiple methods exist, their application in forest plants requires further research. Therefore, this study focused on the effect of disinfection, leaf development and phytohormones on callus induction in Simarouba amara. The study was structured in two experiments. In the first experiment, the efficacy of leaflet disinfection was evaluated using a completely randomized design with three sodium hypochlorite treatments (0 %, 0.25 % and 0.5 %). The second experiment, focused on callus induction, was developed under a 3 x 6 factorial design, which included three stages of leaf development (young, intermediate and mature) and six combinations of phytohormones (BAP, TDZ, 2,4-D, BAP+TDZ, BAP+2,4-D, TDZ+2,4-D, all at 1 mg/L). The main results showed that 0.25 % sodium hypochlorite achieved 88.9 % asepsis, with a lower percentage of oxidation (17 %). It was observed that, combinations of BAP+2,4-D and TDZ+2,4-D promoted higher callus formation, increased callus area and fresh and dry matter production, especially in segments of intermediate leaf development stage. This study highlights the importance of adjusting disinfectant and phytohormones according to leaf development stage for successful callus induction in Simarouba amara.