Cyperus esculentus produces large amounts of oil as one of the main oil storage reserves in underground tubers, making this crop species not only a promising resource for edible oil and biofuel in food and chemical industry, but also a model system for studying oil accumulation in non-seed tissues. In this study, we determined the chloroplast genome sequence of the cultivated C. esculentus (var. sativus Boeckeler). The results showed that the complete chloroplast genome of C. esculentus was 186,255 bp in size, and possessed a typical quadripartite structure containing one large single copy (100,940 bp) region, one small single copy (10,439 bp) region, and a pair of inverted repeat regions of 37,438 bp in size. Sequence analyses indicated that the chloroplast genome encodes 141 genes, including 93 protein-coding genes, 40 transfer RNA genes, and 8 ribosomal RNA genes. We also identified 396 simple-sequence repeats and 49 long repeats, including 15 forward repeats and 34 palindromes within the chloroplast genome of C. esculentus. Most of these repeats were distributed in the noncoding regions. Whole chloroplast genome comparison with those of the other four Cyperus species indicated that both the large single copy and inverted repeat regions were more divergent than the small single copy region, with the highest variation found in the inverted repeat regions. In the phylogenetic trees based on the complete chloroplast genomes of 13 species, all five Cyperus species within the Cyperaceae formed a clade, and C. esculentus was evolutionarily more related to C. rotundus than to the other three Cyperus species. In summary, the chloroplast genome sequence of the cultivated C. esculentus provides a valuable genomic resource for species identification, evolution, and comparative genomic research on this crop species and other Cyperus species in the Cyperaceae family.

Background: Lipid droplets (LDs) present in land plants serve as an essential energy and carbon reserve for seed germination and seedling development. Oleosins, the most abundant structural proteins of LDs, comprise a small family involved in LD formation, stabilization and degradation. Despite their importance, our knowledge on oleosins is still poor in Euphorbiaceae, a large plant family that contains several important oil-bearing species. Results: To uncover lineage-specific evolution of oleosin genes in Euphorbiaceae, in this study, we performed a genome-wide identification and comprehensive comparison of the oleosin family in Euphorbiaceae species with available genome sequences, i.e. castor bean (Ricinus communis), physic nut (Jatropha curcas), tung tree (Vernicia fordii), Mercurialis annua, cassava (Manihot esculenta) and rubber tree (Hevea brasiliensis), and a number of five, five, five, five, eight and eight members were found, respectively. Synteny analysis revealed one-to-one collinear relationship of oleosin genes between the former four (i.e. castor bean, physic nut, tung tree and M. annua) as well as latter two species (i.e. cassava and rubber tree), whereas one-to-one and one-to-two collinear relationships were observed between physic nut and cassava, reflecting the occurrence of one recent whole-genome duplication (WGD) in the last common ancestor of cassava and rubber tree. The presence of five ortholog groups representing three previously defined clades (i.e. U, SL and SH) dates back at least to the Malpighiales ancestor, because they are also conserved in poplar (Populus trichocarpa), a tree having experienced one Salicaceae-specific recent WGD. As observed in poplar, WGD was shown to be the main driver for the family expansion in both cassava and rubber tree. Nevertheless, same retention patterns of WGD-derived duplicates observed in cassava and rubber tree are somewhat different from that of poplar, though certain homologous fragments are still present in rubber tree. Further transcriptional profiling revealed an apparent seed-predominant expression pattern of oleosin genes in physic nut, castor bean and rubber tree. Moreover, structure and expression divergence of paralogous pairs were also observed in both cassava and rubber tree. Conclusion: Comparative genomics analysis of oleosin genes reported in this study improved our knowledge on lineage-specific family evolution in Euphorbiaceae, which also provides valuable information for further functional analysis and utilization of key members and their promoters.

Background: Tonoplast intrinsic proteins (TIPs), which typically mediate water transport across vacuolar membranes, play an essential role in plant growth, development, and stress responses. However, their characterization in tigernut (Cyperus esculentus L.), an oil-bearing tuber plant of the Cyperaceae family, is still in the infancy. Results: In this study, a first genome-wide characterization of the TIP subfamily was conducted in tigernut, resulting in ten members representing five previously defined phylogenetic groups, i.e., TIP1–5. Although the gene amounts are equal to that present in two model plants Arabidopsis and rice, the group composition and/or evolution pattern were shown to be different. Except for CeTIP1;3 that has no counterpart in both Arabidopsis and rice, complex orthologous relationships of 1:1, 1:2, 1:3, 2:1, and 2:2 were observed. Expansion of the CeTIP subfamily was contributed by whole-genome duplication (WGD), transposed, and dispersed duplications. In contrast to the recent WGD-derivation of CeTIP3;1/-3;2, synteny analyses indicated that TIP4 and − 5 are old WGD repeats of TIP2, appearing sometime before monocot-eudicot divergence. Expression analysis revealed that CeTIP genes exhibit diverse expression profiles and are subjected to developmental and diurnal fluctuation regulation. Moreover, when transiently overexpressed in tobacco leaves, CeTIP1;1 was shown to locate in the vacuolar membrane and function in homo/heteromultimer, whereas CeTIP2;1 is located in the cell membrane and only function in heteromultimer. Interestingly, CeTIP1;1 could mediate the tonoplast-localization of CeTIP2;1 via protein interaction, implying complex regulatory patterns. Conclusions: Our findings provide a global view of CeTIP genes, which provide valuable information for further functional analysis and genetic improvement through manipulating key members in tigernut.

Transposable elements (TEs) are abundant components of plant genomes, yet their transcriptional activity and potential biological roles remain underexplored, especially under environmental stress conditions. This study investigates the transcriptional dynamics of TEs in Brassica napus during drought stress in seed development, aiming to uncover their contributions to stress responses and seed germination. RNA-seq data were analyzed for TE transcriptional activity in wild-type (WT) and BnaABI5 CRISPR-edited mutant lines of B. napus. A comprehensive computational pipeline was used to identify and characterize TE-derived transcripts, including protein-coding and long non-coding RNAs (lncRNAs). Functional annotation was performed for protein-coding TE transcripts located in intergenic regions to predict their involvement in biological processes. Out of 212,800 TEs identified in the B. napus genome, 17,547 were transcriptionally active, yielding 15,808 protein-coding transcripts and 1,739 lncRNAs. Among these, 65 protein-coding TE transcripts were identified as transposase genes, while 860 transcripts were predicted to represent novel genes derived from transposon regions, potentially participating in monocarboxylic acid metabolic processes. Specific to drought stress responses during seed germination, 128 protein-coding TE transcripts (including 5 transposases) and 37 lncRNAs were differentially expressed. Notably, the lncRNA transcripts MSTRG.108925.4 and MSTRG.109003.7 were implicated in regulating the PHD finger protein ALFIN-LIKE 1 (BnA10g0418090), contributing to drought tolerance mechanisms. This study highlights the functional relevance of TE transcription in the context of drought stress during seed germination, providing novel insights into TE-derived genes and lncRNAs as potential regulators of stress responses. These findings expand the understanding of TE biology in plants and offer valuable resources for future efforts to identify drought-resistant genes in B. napus.