Non-coding RNAs having strong positive interaction with mRNAs reveal their regulatory nature during flowering in a wild relative of pigeonpea (Cajanus scarabaeoides)

Genome-wide characterization of drought-responsive long non-coding RNAs in sorghum (Sorghum bicolor)

Drought stress strongly affects crop yield. Although knowledge of long non-coding RNAs (lncRNAs) has been updated continuously and rapidly, information about lncRNAs in drought resistance regulation is extremely limited in sorghum. Here, lncRNA-sequencing was performed with seedlings of a sorghum cultivar (Jinza29) under three water control treatments to investigate the mechanism of lncRNAs responsible for drought resistance in sorghum. A total of 377 differentially expressed lncRNAs (DElncRNAs) were identified. We also predicted 4322 and 2827 transcripts as potential cis-target and trans-target genes for drought-responsive lncRNAs, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that those target genes exhibited marked enrichment into "oxidoreductase activity", "signal transducer activity", "DNA repair", "photosynthesis", "glutathione metabolism", and "phenylpropanoid biosynthesis" and other terms associated with abiotic stress resistance. Moreover, several lncRNAs were estimated to modulate the expression of other genes related to stress response and photosynthetic carbon metabolism. Additionally, we found 107 DElncRNAs that might be candidate target mimics for 56 miRNAs. LncRNAs play important roles in drought adaptation of sorghum through interacting with protein-encoding genes. The obtained results provided novel insights into the biological characteristics of lncRNAs and offered potential regulatory factors for genetically enhancing drought resistance in sorghum.

Identification of superior haplotypes for flowering time in pigeonpea through candidate gene-based association study of a diverse minicore collection

KEY MESSAGE

In current study candidate gene (261 genes) based association mapping on 144 pigeonpea accessions for flowering time and related traits and 29 MTAs producing eight superior haplotypes were identified. In the current study, we have conducted an association analysis for flowering-associated traits in a diverse pigeonpea mini-core collection comprising 144 accessions using the SNP data of 261 flowering-related genes. In total, 13,449 SNPs were detected in the current study, which ranged from 743 (ICP10228) to 1469 (ICP6668) among the individuals. The nucleotide diversity (0.28) and Watterson estimates (0.34) reflected substantial diversity, while Tajima's D (-0.70) indicated the abundance of rare alleles in the collection. A total of 29 marker trait associations (MTAs) were identified, among which 19 were unique to days to first flowering (DOF) and/or days to fifty percent flowering (DFF), 9 to plant height (PH), and 1 to determinate (Det) growth habit using 3 years of phenotypic data. Among these MTAs, six were common to DOF and/or DFF, and four were common to DOF/DFF along with the PH, reflecting their pleiotropic action. These 29 MTAs spanned 25 genes, among which 10 genes clustered in the protein-protein network analysis, indicating their concerted involvement in floral induction. Furthermore, we identified eight haplotypes, four of which regulate late flowering, while the remaining four regulate early flowering using the MTAs. Interestingly, haplotypes conferring late flowering (H001, H002, and H008) were found to be taller, while those involved in early flowering (H003) were shorter in height. The expression pattern of these genes, as inferred from the transcriptome data, also underpinned their involvement in floral induction. The haplotypes identified will be highly useful to the pigeonpea breeding community for haplotype-based breeding.

A Survey of Computational Methods and Databases for lncRNA-MiRNA Interaction Prediction

Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are two prevalent non-coding RNAs in current research. They play critical regulatory roles in the life processes of animals and plants. Studies have shown that lncRNAs can interact with miRNAs to participate in post-transcriptional regulatory processes, mainly involved in regulating cancer development, metastatic progression, and drug resistance. Additionally, these interactions have significant effects on plant growth, development, and responses to biotic and abiotic stresses. Deciphering the potential relationships between lncRNAs and miRNAs may provide new insights into our understanding of the biological functions of lncRNAs and miRNAs, and the pathogenesis of complex diseases. In contrast, gathering information on lncRNA-miRNA interactions (LMIs) through biological experiments is expensive and time-consuming. With the accumulation of multi-omics data, computational models are extremely attractive in systematically exploring potential LMIs. To the best of our knowledge, this is the first comprehensive review of computational methods for identifying LMIs. Specifically, we first summarized the available public databases for predicting animal and plant LMIs. Second, we comprehensively reviewed the computational methods for predicting LMIs and classified them into two categories, including network-based methods and sequence-based methods. Third, we analyzed the standard evaluation methods and metrics used in LMI prediction. Finally, we pointed out some problems in the current study and discuss future research directions. Relevant databases and the latest advances in LMI prediction are summarized in a GitHub repository https://github.com/sheng-n/lncRNA-miRNA-interaction-methods, and we'll keep it updated.

Genomic survey of high-throughput RNA-Seq data implicates involvement of long intergenic non-coding RNAs (lincRNAs) in cytoplasmic male-sterility and fertility restoration in pigeon pea

BACKGROUND

Long-intergenic non-coding RNAs (lincRNAs) originate from intergenic regions and have no coding potential. LincRNAs have emerged as key players in the regulation of various biological processes in plant development. Cytoplasmic male-sterility (CMS) in association with restorer-of-fertility (Rf) systems makes it a highly reliable tool for exploring heterosis for producing commercial hybrid seeds. To date, there have been no reports of lincRNAs during pollen development in CMS and fertility restorer lines in pigeon pea.

OBJECTIVE

Identification of lincRNAs in the floral buds of cytoplasmic male-sterile (AKCMS11) and fertility restorer (AKPR303) pigeon pea lines.

METHODS

We employed a computational approach to identify lincRNAs in the floral buds of cytoplasmic male-sterile (AKCMS11) and fertility restorer (AKPR303) pigeon pea lines using RNA-Seq data.

RESULTS

We predicted a total of 2145 potential lincRNAs of which 966 were observed to be differentially expressed between the sterile and fertile pollen. We identified, 927 cis-regulated and 383 trans-regulated target genes of the lincRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the target genes revealed that these genes were specifically enriched in pathways like pollen and pollen tube development, oxidative phosphorylation, etc. We detected 23 lincRNAs that were co-expressed with 17 pollen-related genes with known functions. Fifty-nine lincRNAs were predicted to be endogenous target mimics (eTMs) for 25 miRNAs, and found to be associated with pollen development. The, lincRNA regulatory networks revealed that different lincRNA-miRNA-mRNA networks might be associated with CMS and fertility restoration.

CONCLUSION

Thus, this study provides valuable information by highlighting the functions of lincRNAs as regulators during pollen development in pigeon pea and utilization in hybrid seed production.

Genome-wide analysis of long non-coding RNAs in sugar beet (Beta vulgaris L.) under drought stress

Drought stress is one of the most severe abiotic stresses that restrict global crop production. Long non-coding RNAs (lncRNAs) have been proved to play a key role in response to drought stress. However, genome-wide identification and characterization of drought-responsive lncRNAs in sugar beet is still lacking. Thus, the present study focused on analyzing lncRNAs in sugar beet under drought stress. We identified 32017 reliable lncRNAs in sugar beet by strand-specific high-throughput sequencing. A total of 386 differentially expressed lncRNAs (DElncRNAs) were found under drought stress. The most significantly upregulated and downregulated lncRNAs were TCONS_00055787 (upregulated by more than 6000 fold) and TCONS_00038334 (downregulated by more than 18000 fold), respectively. Quantitative real-time PCR results exhibited a high concordance with RNA sequencing data, which conformed that the expression patterns of lncRNAs based on RNA sequencing were highly reliable. In addition, we predicted 2353 and 9041 transcripts that were estimated to be the cis- and trans-target genes of the drought-responsive lncRNAs. As revealed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the target genes of DElncRNAs were significantly enriched in organelle subcompartment, thylakoid, endopeptidase activity, catalytic activity, developmental process, lipid metabolic process, RNA polymerase activity, transferase activity, flavonoid biosynthesis and several other terms associated with abiotic stress tolerance. Moreover, 42 DElncRNAs were predicted as potential miRNA target mimics. LncRNAs have important effects on plant adaptation to drought conditions through the interaction with protein-encoding genes. The present study leads to greater insights into lncRNA biology and offers candidate regulators for improving the drought tolerance of sugar beet cultivars at the genetic level.

Evolutionary expansion and expression dynamics of cytokinin-catabolizing CKX gene family in the modern amphidiploid mustard (Brassica sp.)

Plant cytokinins (CKs) promote development and physiological processes, drought tolerance, root architecture, and ultimately crop productivity. Biologically active CKs (iP, tZ, and cZ) are precisely maintained in the vegetative and floral tissues through their irreversible degradation by developmentally regulated CK-catabolizing cytokinin oxidase/dehydrogenase (CKX) enzyme. A meta-analysis of CKX proteins was performed through an exhaustive exploration of multiple genome databases of cyanobacteria, bryophyte, monocot and eudicot plants to reveal the intricate evolutionary profiles of CKX enzymes specific to the family Brassicaceae. At least 175 unique paralogous/orthologous CKX sequences were successfully retrieved and phylogenetically clustered into distinct groups. Observations of structural divergences among paralogous sequences compared to their orthologs indicated that the progenitor CKX sequence had been subjected to massive structural modifications, possibly as a result of the evolutionary split between monocots and eudicots. An analysis of dN/dS comparisons of orthologous genes revealed that segmental CKX gene duplications have evolved primarily under purifying selection. Further, 24 CKX genes with conserved signature domain were identified in the amphidiploid Brassica juncea genome (AABB; 2n = 36). Genetic evolution of paralogous and orthologous genes was largely responsible for the expansion of CKX homoeologs in the amphidiploid Brassica genomes. Also, comparative analyses of 1.5 kb-long upstream regulatory regions of BjCKX genes identified various development- and stress-responsive elements. Spatial and temporal expression profiles of CKX genes were primarily attributed to their structural diversity observed in the 5'-regulatory regions along with species evolution. This data suggested that CKX duplicate genes had partitioned their spatial expression (= function) during evolution. These findings illustrated the evolutionary importance of CKX genes during plant development, and also suggested their deployment for future crop improvement programs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03294-0.

Single trait versus principal component based association analysis for flowering related traits in pigeonpea

Pigeonpea, a tropical photosensitive crop, harbors significant diversity for days to flowering, but little is known about the genes that govern these differences. Our goal in the current study was to use genome wide association strategy to discover the loci that regulate days to flowering in pigeonpea. A single trait as well as a principal component based association study was conducted on a diverse collection of 142 pigeonpea lines for days to first and fifty percent of flowering over 3 years, besides plant height and number of seeds per pod. The analysis used seven association mapping models (GLM, MLM, MLMM, CMLM, EMLM, FarmCPU and SUPER) and further comparison revealed that FarmCPU is more robust in controlling both false positives and negatives as it incorporates multiple markers as covariates to eliminate confounding between testing marker and kinship. Cumulatively, a set of 22 SNPs were found to be associated with either days to first flowering (DOF), days to fifty percent flowering (DFF) or both, of which 15 were unique to trait based, 4 to PC based GWAS while 3 were shared by both. Because PC1 represents DOF, DFF and plant height (PH), four SNPs found associated to PC1 can be inferred as pleiotropic. A window of ± 2 kb of associated SNPs was aligned with available transcriptome data generated for transition from vegetative to reproductive phase in pigeonpea. Annotation analysis of these regions revealed presence of genes which might be involved in floral induction like Cytochrome p450 like Tata box binding protein, Auxin response factors, Pin like genes, F box protein, U box domain protein, chromatin remodelling complex protein, RNA methyltransferase. In summary, it appears that auxin responsive genes could be involved in regulating DOF and DFF as majority of the associated loci contained genes which are component of auxin signaling pathways in their vicinity. Overall, our findings indicates that the use of principal component analysis in GWAS is statistically more robust in terms of identifying genes and FarmCPU is a better choice compared to the other aforementioned models in dealing with both false positive and negative associations and thus can be used for traits with complex inheritance.

Genome-wide transcriptome analysis and characterization of the cytochrome P450 flavonoid biosynthesis genes in pigeon pea (Cajanus cajan)

226 CcCYP450 genes were identified at the genomic level and were classified into 45 clades based on phylogenetic analysis. CcCYP75B165 gene was found that might play important roles in the biosynthesis of flavonoids in pigeon pea, and was significantly induced by methyl jasmonate (MeJA). The cytochrome P450 mono-oxygenase (CYP450) superfamily plays a key role in the flavonoid biosynthesis pathway and resists different kinds of stresses. Several CYP450 genes have been identified to be involved in the biosynthesis of crop protection agents. However, the CcCYP450 genes from pigeon pea have not been identified. Here, 226 CcCYP450 genes were identified at the genomic level by analysing the gene structure, distribution on chromosomes, gene duplication, and conserved motifs and were classified into 45 clades based on phylogenetic analysis. RNA-seq analysis revealed clear details of CcCYP450 genes that varied with time of MeJA (methyl jasmonate) induction. Among them, six CcCYP450 subfamily genes were found that might play important roles in the biosynthesis of flavonoids in pigeon pea. The overexpression of CcCYP75B165 in pigeon pea significantly induced the accumulation of genistin and downregulated the contents of cajaninstilbene acid, apigenin, isovitexin, and genistein and the expression of flavonoid synthase genes. This study provides theoretical guidance and plant genetic resources for cultivating new pigeon pea varieties with high flavonoid contents and exploring the molecular mechanisms of the biosynthesis of flavonoids under MeJA treatment.

The Characters of Non-Coding RNAs and Their Biological Roles in Plant Development and Abiotic Stress Response

Plant growth and development are greatly affected by the environment. Many genes have been identified to be involved in regulating plant development and adaption of abiotic stress. Apart from protein-coding genes, more and more evidence indicates that non-coding RNAs (ncRNAs), including small RNAs and long ncRNAs (lncRNAs), can target plant developmental and stress-responsive mRNAs, regulatory genes, DNA regulatory regions, and proteins to regulate the transcription of various genes at the transcriptional, posttranscriptional, and epigenetic level. Currently, the molecular regulatory mechanisms of sRNAs and lncRNAs controlling plant development and abiotic response are being deeply explored. In this review, we summarize the recent research progress of small RNAs and lncRNAs in plants, focusing on the signal factors, expression characters, targets functions, and interplay network of ncRNAs and their targets in plant development and abiotic stress responses. The complex molecular regulatory pathways among small RNAs, lncRNAs, and targets in plants are also discussed. Understanding molecular mechanisms and functional implications of ncRNAs in various abiotic stress responses and development will benefit us in regard to the use of ncRNAs as potential character-determining factors in molecular plant breeding.

LncRNA TCONS_00021861 is functionally associated with drought tolerance in rice (Oryza sativa L.) via competing endogenous RNA regulation

BACKGROUND

Water deficit is an abiotic stress that retards plant growth and destabilizes crop production. Long non coding RNAs (lncRNAs) are a class of non-coding endogenous RNAs that participate in diverse cellular processes and stress responses in plants. lncRNAs could function as competing endogenous RNAs (ceRNA) and represent a novel layer of gene regulation. However, the regulatory mechanism of lncRNAs as ceRNA in drought stress response is yet unclear.

RESULTS

In this study, we performed transcriptome-wide identification of drought-responsive lncRNAs in rice. Thereafter, we constructed a lncRNA-mediated ceRNA network by analyzing competing relationships between mRNAs and lncRNAs based on ceRNA hypothesis. A drought responsive ceRNA network with 40 lncRNAs, 23 miRNAs and 103 mRNAs was obtained. Network analysis revealed TCONS_00021861/miR528-3p/YUCCA7 regulatory axis as a hub involved in drought response. The miRNA-target expression and interaction were validated by RT-qPCR and RLM-5'RACE. TCONS_00021861 showed significant positive correlation (r = 0.7102) with YUCCA7 and negative correlation with miR528-3p (r = -0.7483). Overexpression of TCONS_00021861 attenuated the repression of miR528-3p on YUCCA7, leading to increased IAA (Indole-3-acetic acid) content and auxin overproduction phenotypes.

CONCLUSIONS

TCONS_00021861 could regulate YUCCA7 by sponging miR528-3p, which in turn activates IAA biosynthetic pathway and confer resistance to drought stress. Our findings provide a new perspective of the regulatory roles of lncRNAs as ceRNAs in drought resistance of rice.

Genome-Wide Changes of Regulatory Non-Coding RNAs Reveal Pollen Development Initiated at Ecodormancy in Peach

Bud dormancy is under the regulation of complex mechanisms including genetic and epigenetic factors. To study the function of regulatory non-coding RNAs in winter dormancy release, we analyzed the small RNA and long non-coding RNA (lncRNA) expression from peach (Prunus persica) floral buds in endodormancy, ecodormancy and bud break stages. Small RNAs underwent a major shift in expression primarily between dormancy and flowering with specific pairs of microRNAs and their mRNA target genes undergoing coordinated differential expression. From endodormancy to ecodormancy, ppe-miR6285 was significantly upregulated while its target gene, an ASPARAGINE-RICH PROTEIN involved in the regulation of abscisic acid signaling, was downregulated. At ecodormancy, ppe-miR2275, a homolog of meiosis-specific miR2275 across angiosperms, was significantly upregulated, supporting microsporogenesis in anthers at a late stage of dormancy. The expression of 785 lncRNAs, unlike the overall expression pattern in the small RNAs, demonstrated distinctive expression signatures across all dormancy and flowering stages. We predicted that a subset of lncRNAs were targets of microRNAs and found 18 lncRNA/microRNA target pairs with both differentially expressed across time points. The genome-wide differential expression and network analysis of non-coding RNAs and mRNAs from the same tissues provide new candidate loci for dormancy regulation and suggest complex noncoding RNA interactions control transcriptional regulation across these key developmental time points.

Genotyping by RAD Sequencing Analysis Assessed the Genetic Distinctiveness of Experimental Lines and Narrowed Down the Genomic Region Responsible for Leaf Shape in Endive (Cichorium endivia L.)

The characterization of genetic diversity in elite breeding stocks is crucial for the registration and protection of new varieties. Moreover, experimental population structure analysis and information about the genetic distinctiveness of commercial materials are essential for crop breeding programs. The purpose of our research was to assess the genetic relationships of 32 endive (Cichorium endivia L.) breeding lines, 18 from var. latifolium (escarole) and 14 from var. crispum (curly), using heterologous Cichorium intybus-derived simple sequence repeats (SSR) markers and single-nucleotide polymorphisms (SNP) markers. We found that 14 out of 29 SSR markers were successfully amplified, but only 8 of them were related to polymorphic loci. To overcome the limitation of the low number of informative SSR marker loci, an alternative SNP-based approach was employed. The 4621 SNPs produced by a restriction site-associated DNA marker sequencing approach were able to fully discriminate the 32 endive accessions; most importantly, as many as 50 marker loci were found to distinguish the curly group from the escarole group. Interestingly, 24 of the marker loci mapped within a peripheral segment of chromosome 8 of lettuce (Lactuca sativa L.), spanning a chromosomal region of 49.6 Mb. Following Sanger sequencing-based validation, three genes were determined to carry nonsynonymous SNPs, and one of them matched a putative ortholog of AtELP1, subunit 1 of the Elongator complex. Considering that several previously characterized Elongator complex subunit mutants exhibited elongated and/or curly leaf phenotypes, this gene should be taken into consideration for a better understanding of the underlying mechanism controlling leaf shape in endive.