ABSTRACT
Background: Sugarcane cultivars are polyploid interspecific hybrids of giant genomes, typically with 10–13 sets of chromosomes from 2 Saccharum species. The ploidy, hybridity, and size of the genome, estimated to have >10 Gb, pose a challenge for sequencing. Results: Here we present a gene space assembly of SP80-3280, including 373,869 putative genes and their potential regulatory regions. The alignment of single-copy genes in diploid grasses to the putative genes indicates that we could resolve 2–6 (up to 15) putative homo(eo)logs that are 99.1% identical within their coding sequences. Dissimilarities increase in their regulatory regions, and gene promoter analysis shows differences in regulatory elements within gene families that are expressed in a species-specific manner. We exemplify these differences for sucrose synthase (SuSy) and phenylalanine ammonia-lyase (PAL), 2 gene families central to carbon partitioning. SP80-3280 has particular regulatory elements involved in sucrose synthesis not found in the ancestor Saccharum spontaneum. PAL regulatory elements are found in co-expressed genes related to fiber synthesis within gene networks defined during plant growth and maturation. Comparison with sorghum reveals predominantly bi-allelic variations in sugarcane, consistent with the formation of 2 "subgenomes" after their divergence ~3.8–4.6 million years ago and reveals single-nucleotide variants that may underlie their differences. Conclusions: This assembly represents a large step towards a whole-genome assembly of a commercial sugarcane cultivar. It includes a rich diversity of genes and homo(eo)logous resolution for a representative fraction of the gene space, relevant to improve biomass and food production.
ABSTRACT
Background: Sugarcane cultivars are polyploid interspecific hybrids of giant genomes, typically with 10–13 sets of chromosomes from 2 Saccharum species. The ploidy, hybridity, and size of the genome, estimated to have >10 Gb, pose a challenge for sequencing. Results: Here we present a gene space assembly of SP80-3280, including 373,869 putative genes and their potential regulatory regions. The alignment of single-copy genes in diploid grasses to the putative genes indicates that we could resolve 2–6 (up to 15) putative homo(eo)logs that are 99.1% identical within their coding sequences. Dissimilarities increase in their regulatory regions, and gene promoter analysis shows differences in regulatory elements within gene families that are expressed in a species-specific manner. We exemplify these differences for sucrose synthase (SuSy) and phenylalanine ammonia-lyase (PAL), 2 gene families central to carbon partitioning. SP80-3280 has particular regulatory elements involved in sucrose synthesis not found in the ancestor Saccharum spontaneum. PAL regulatory elements are found in co-expressed genes related to fiber synthesis within gene networks defined during plant growth and maturation. Comparison with sorghum reveals predominantly bi-allelic variations in sugarcane, consistent with the formation of 2 "subgenomes" after their divergence ~3.8–4.6 million years ago and reveals single-nucleotide variants that may underlie their differences. Conclusions: This assembly represents a large step towards a whole-genome assembly of a commercial sugarcane cultivar. It includes a rich diversity of genes and homo(eo)logous resolution for a representative fraction of the gene space, relevant to improve biomass and food production.
ABSTRACT
Leptospira interrogans serovar Copenhageni is a human pathogen that causes leptospirosis, a worldwide zoonosis. The L. interrogans genome codes for a wide array of potential diguanylate cyclase (DGC) enzymes with characteristic GGDEF domains capable of synthesizing the cyclic dinucleotide c-di-GMP, known to regulate transitions between different cellular behavioral states in bacteria. Among such enzymes, LIC13137 (Lcd1), which has an N-terminal cGMP-specific phosphodiesterases, adenylyl cyclases, and FhIA (GAF) domain and a C-terminal GGDEF domain, is notable for having close orthologs present only in pathogenic Leptospira species. Although the function and structure of GGDEF and GAF domains have been studied extensively separately, little is known about enzymes with the GAF-GGDEF architecture. In this report, we address the question of how the GAF domain regulates the DGC activity of Lcd1. The full-length Lcd1 and its GAF domain form dimers in solution. The GAF domain binds specifically cAMP (K-D of 0.24 mu M) and has an important role in the regulation of the DGC activity of the GGDEF domain. Lcd1 DGC activity is negligible in the absence of cAMP and is significantly enhanced in its presence (specific activity of 0.13 s(-1)). The crystal structure of the Lcd1 GAF domain in complex with cAMP provides valuable insights toward explaining its specificity for cAMP and pointing to possible mechanisms by which this cyclic nucleotide regulates the assembly of an active DGC enzyme.
