Rosales sister to Fabales: towards resolving the rosid puzzle

Transcriptome analysis of mulberry (Morus alba L.) leaves to identify differentially expressed genes associated with post-harvest shelf-life elongation

Present study deals with molecular expression patterns responsible for post-harvest shelf-life extension of mulberry leaves. Quantitative profiling showed retention of primary metabolite and accumulation of stress markers in NS7 and CO7 respectively. The leaf mRNA profiles was sequenced using the Illumina platform to identify DEGs. A total of 3413 DEGs were identified between the treatments. Annotation with Arabidopsis database has identified 1022 DEGs unigenes. STRING generated protein-protein interaction, identified 1013 DEGs nodes with p < 1.0e-16. KEGG classifier has identified genes and their participating biological processes. MCODE and BiNGO detected sub-networking and ontological enrichment, respectively at p ≤ 0.05. Genes associated with chloroplast architecture, photosynthesis, detoxifying ROS and RCS, and innate-immune response were significantly up-regulated, responsible for extending shelf-life in NS7. Loss of storage sucrose, enhanced activity of senescence-related hormones, accumulation of xenobiotics, and development of osmotic stress inside tissue system was the probable reason for tissue deterioration in CO7. qPCR validation of DEGs was in good agreement with RNA sequencing results, indicating the reliability of the sequencing platform. Present outcome provides a molecular insight regarding involvement of genes in self-life extension, which might help the sericulture industry to overcome their pre-existing problems related to landless farmers and larval feeding during monsoon.

Draft genome sequence of Indian mulberry (Morus indica) provides a resource for functional and translational genomics

Mulberry is an important crop plant for the sericulture industry. Here, we report high-quality genome sequence of a cultivated Indian mulberry (Morus indica cv K2) obtained by combining data from four different technologies, including Illumina, single-molecule real-time sequencing, chromosome conformation capture and optical mapping, with a gene completeness of 96.5%. Based on the genome sequence, we identified 49.2% of repetitive DNA and 27,435 high-confidence protein-coding genes with >90% of them supported by transcript evidence. A comparative analysis with other plant genomes identified 4.8% of species-specific genes in the M. indica genome. Transcriptome profiling revealed tissue-specific and differential expression across multiple accessions of ~4.7% and 2-5% of protein-coding genes, respectively, implicated in diverse biological processes. Whole genome resequencing of 21 accessions/species revealed ~2.5 million single nucleotide polymorphisms and ~ 0.2 million insertions/deletions. These data and results provide a comprehensive resource to accelerate the genomics research in mulberry for its improvement.

Electrochemistry-based chemotaxonomy in plants using the voltammetry of microparticles methodology

Characterization of vegetal taxa is achievedviacharacteristic voltammetric features displayed by leaf extracts.

The advent of genomics in mulberry and perspectives for productivity enhancement

Sericulture in India is a highly remunerative industry, especially for the rural population. Mulberry is an extremely versatile plant, having multifaceted applications, the most important being the sole feed for the monophagus silkworm, Bombyx mori. Profitability of the sericulture industry is directly correlated with production of high-quality mulberry leaves. However, mulberry productivity is severely impacted by abiotic as well as biotic stresses. Therefore, to develop stress-tolerant mulberry with desired characteristics, a comprehensive understanding and utility of biotechnological resources is essential. Research efforts on mulberry encompass broad range of fields in plant biology from breeding, molecular markers, transcriptomics, proteomics, and metabolomics. Additionally, a large number of mulberry germplasm accessions have been maintained and evaluated in several countries. Identification of superior cultivars under stressed regimes is extremely important, and therefore, physiological traits have often been used as proxy genetic markers for assessing stress tolerance index. Mulberry genomic resources have provided a limited but an important list of novel candidate genes, thus enhancing the scope for future investigations for improvement of its productivity. The present review article gives a bird's eye view of current initiatives of genomics advancements in mulberry research and enumerates the prospects for enhancing its productivity.

Multi-gene analysis provides a well-supported phylogeny of Rosales

Despite many attempts to resolve evolutionary relationships among the major clades of Rosales, some nodes have been extremely problematic and have remained unresolved. In this study, we use two nuclear and 10 plastid loci to infer phylogenetic relationships among all nine families of Rosales. Rosales were strongly supported as monophyletic; within Rosales all family relationships are well-supported with Rosaceae sister to all other members of the order. Remaining Rosales can be divided into two subclades: (1) Ulmaceae are sister to Cannabaceae plus (Urticaceae+Moraceae); (2) Rhamnaceae are sister to Elaeagnaceae plus (Barbeyaceae+Dirachmaceae). One noteworthy result is that we recover the first strong support for a sister relationship between the enigmatic Dirachmaceae and Barbeyaceae. These two small families have distinct morphologies and potential synapomorphies remain unclear. Future studies should try to identify nonDNA synapomorphies uniting Barbeyaceae with Dirachmaceae.

Polyploidy did not predate the evolution of nodulation in all legumes

BACKGROUND

Several lines of evidence indicate that polyploidy occurred by around 54 million years ago, early in the history of legume evolution, but it has not been known whether this event was confined to the papilionoid subfamily (Papilionoideae; e.g. beans, medics, lupins) or occurred earlier. Determining the timing of the polyploidy event is important for understanding whether polyploidy might have contributed to rapid diversification and radiation of the legumes near the origin of the family; and whether polyploidy might have provided genetic material that enabled the evolution of a novel organ, the nitrogen-fixing nodule. Although symbioses with nitrogen-fixing partners have evolved in several lineages in the rosid I clade, nodules are widespread only in legume taxa, being nearly universal in the papilionoids and in the mimosoid subfamily (e.g., mimosas, acacias)--which diverged from the papilionoid legumes around 58 million years ago, soon after the origin of the legumes.

METHODOLOGY/PRINCIPAL FINDINGS

Using transcriptome sequence data from Chamaecrista fasciculata, a nodulating member of the mimosoid clade, we tested whether this species underwent polyploidy within the timeframe of legume diversification. Analysis of gene family branching orders and synonymous-site divergence data from C. fasciculata, Glycine max (soybean), Medicago truncatula, and Vitis vinifera (grape; an outgroup to the rosid taxa) establish that the polyploidy event known from soybean and Medicago occurred after the separation of the mimosoid and papilionoid clades, and at or shortly before the Papilionoideae radiation.

CONCLUSIONS

The ancestral legume genome was not fundamentally polyploid. Moreover, because there has not been an independent instance of polyploidy in the Chamaecrista lineage there is no necessary connection between polyploidy and nodulation in legumes. Chamaecrista may serve as a useful model in the legumes that lacks a paleopolyploid history, at least relative to the widely studied papilionoid models.

Mitochondrial matR sequences help to resolve deep phylogenetic relationships in rosids

Background

Rosids are a major clade in the angiosperms containing 13 orders and about one-third of angiosperm species. Recent molecular analyses recognized two major groups (i.e., fabids with seven orders and malvids with three orders). However, phylogenetic relationships within the two groups and among fabids, malvids, and potentially basal rosids including Geraniales, Myrtales, and Crossosomatales remain to be resolved with more data and a broader taxon sampling. In this study, we obtained DNA sequences of the mitochondrial matR gene from 174 species representing 72 families of putative rosids and examined phylogenetic relationships and phylogenetic utility of matR in rosids. We also inferred phylogenetic relationships within the "rosid clade" based on a combined data set of 91 taxa and four genes including matR, two plastid genes (rbcL, atpB), and one nuclear gene (18S rDNA).

Results

Comparison of mitochondrial matR and two plastid genes (rbcL and atpB) showed that the synonymous substitution rate in matR was approximately four times slower than those of rbcL and atpB; however, the nonsynonymous substitution rate in matR was relatively high, close to its synonymous substitution rate, indicating that the matR has experienced a relaxed evolutionary history. Analyses of our matR sequences supported the monophyly of malvids and most orders of the rosids. However, fabids did not form a clade; instead, the COM clade of fabids (Celastrales, Oxalidales, Malpighiales, and Huaceae) was sister to malvids. Analyses of the four-gene data set suggested that Geraniales and Myrtales were successively sister to other rosids, and that Crossosomatales were sister to malvids.

Conclusion

Compared to plastid genes such as rbcL and atpB, slowly evolving matR produced less homoplasious but not less informative substitutions. Thus, matR appears useful in higher-level angiosperm phylogenetics. Analysis of matR alone identified a novel deep relationship within rosids, the grouping of the COM clade of fabids and malvids, which was not resolved by any previous molecular analyses but recently suggested by floral structural features. Our four-gene analysis supported the placements of Geraniales, Myrtales at basal nodes of the rosid clade and placed Crossosomatales as sister to malvids. We also suggest that the core part of rosids should include fabids, malvids and Crossosomatales.