Genome-wide analysis and molecular dissection of the SPL gene family in Salvia miltiorrhiza

Genome-Wide Identification and Functional Analysis of Salvia miltiorrhiza MicroRNAs Reveal the Negative Regulatory Role of Smi-miR159a in Phenolic Acid Biosynthesis

MicroRNAs (miRNAs) are a group of endogenous small non-coding RNAs in plants. They play critical functions in various biological processes during plant growth and development. Salvia miltiorrhiza is a well-known traditional Chinese medicinal plant with significant medicinal, economic, and academic values. In order to elucidate the role of miRNAs in S. miltiorrhiza, six small RNA libraries from mature roots, young roots, stems, mature leaves, young leaves and flowers of S. miltiorrhiza and one degradome library from mixed tissues were constructed. A total of 184 miRNA precursors, generating 137 known and 49 novel miRNAs, were genome-widely identified. The identified miRNAs were predicted to play diversified regulatory roles in plants through regulating 891 genes. qRT-PCR and 5' RLM-RACE assays validated the negative regulatory role of smi-miR159a in SmMYB62, SmMYB78, and SmMYB80. To elucidate the function of smi-miR159a in bioactive compound biosynthesis, smi-miR159a transgenic hairy roots were generated and analyzed. The results showed that overexpression of smi-miR159a caused a significant decrease in rosmarinic acid and salvianolic acid B contents. qRT-PCR analysis showed that the targets of smi-miR159a, including SmMYB62, SmMYB78, and SmMYB80, were significantly down-regulated, accompanied by the down-regulation of SmPAL1, SmC4H1, Sm4CL1, SmTAT1, SmTAT3, SmHPPR1, SmRAS, and SmCYP98A14 genes involved in phenolic acid biosynthesis. It suggests that smi-miR159a is a significant negative regulator of phenolic acid biosynthesis in S. miltiorrhiza.

The Smi-miR858a-SmMYB module regulates tanshinone and phenolic acid biosynthesis in Salvia miltiorrhiza

Tanshinones and phenolic acids are two major classes of bioactive compounds in Salvia miltiorrhiza. Revealing the regulatory mechanism of their biosynthesis is crucial for quality improvement of S. miltiorrhiza medicinal materials. Here we demonstrated that Smi-miR858a-Smi-miR858c, a miRNA family previously known to regulate flavonoid biosynthesis, also played critical regulatory roles in tanshinone and phenolic acid biosynthesis in S. miltiorrhiza. Overexpression of Smi-miR858a in S. miltiorrhiza plants caused significant growth retardation and tanshinone and phenolic acid reduction. Computational prediction and degradome and RNA-seq analyses revealed that Smi-miR858a could directly cleave the transcripts of SmMYB6, SmMYB97, SmMYB111, and SmMYB112. Yeast one-hybrid and transient transcriptional activity assays showed that Smi-miR858a-regulated SmMYBs, such as SmMYB6 and SmMYB112, could activate the expression of SmPAL1 and SmTAT1 involved in phenolic acid biosynthesis and SmCPS1 and SmKSL1 associated with tanshinone biosynthesis. In addition to directly activating the genes involved in bioactive compound biosynthesis pathways, SmMYB6, SmMYB97, and SmMYB112 could also activate SmAOC2, SmAOS4, and SmJMT2 involved in the biosynthesis of methyl jasmonate, a significant elicitor of plant secondary metabolism. The results suggest the existence of dual signaling pathways for the regulation of Smi-miR858a in bioactive compound biosynthesis in S. miltiorrhiza.

Overexpression of MiSPL3a and MiSPL3b confers early flowering and stress tolerance in Arabidopsis thaliana

SQUAMOSA promoter-binding protein-like (SPL) family genes play an important role in regulating plant flowering and resistance to stress. However, understanding the function of the SPL family in mango is still limited. In a previous study, two MiSPL3 genes, MiSPL3a and MiSPL3b (MiSPL3a/b), were identified in 'SiJiMi' mango and exhibited the highest expression in flowers at the initial flowering stage [24]. Therefore, in this study, we further investigated the expression pattern and gene function of MiSPL3a/b. The results showed that the expression of MiSPL3a was greatest at the end of floral bud differentiation, and MiSPL3b was expressed mainly during the flowering induction and vegetative growth stages. Subcellular localization showed that MiSPL3a/b localized to the nucleus. In addition, ectopic expression of MiSPL3a/b promoted earlier flowering in Arabidopsis thaliana by 3 d-6 d than in wild-type (WT) plants, which increased the expression of SUPPRESSOR OF CONSTANS1 (AtSOC1), FRUITFULL (AtFUL), and APETALA1 (AtAP1). MiSPL3a/b transgenic lines exhibited increased tolerance to drought, GA3, and abscisic acid (ABA) treatments but were sensitive to Pro-Ca treatment. Furthermore, protein interaction analysis revealed that MiSPL3a/b could interact with several stress-related proteins, flowering-related proteins, and the bridge protein 14-3-3. Taken together, MiSPL3a and MiSPL3b acted as positive regulators of flowering time and stress tolerance in transgenic Arabidopsis.

Molecular mechanisms of miR172a and its target gene LbrTOE3 regulating maturation in Lilium

MAIN CONCLUSION

Lbr-miR172a could promote the growth phase transition and shorten maturation in Lilium, while LbrTOE3 inhibited this process and prolonged the growth period. Lilium is an ornamental flower with high economic value for both food and medicinal purposes. However, under natural conditions, Lilium bulbs take a long time and cost more to grow to commercial size. This research was conducted to shorten the maturation time by subjecting Lilium bulbs to alternating temperature treatment. To explore the molecular mechanism of the vegetative phase change (VPC) in Lilium after variable temperature treatment, the key module miR172a-TOE3 was selected based on a combined omics analysis. Gene cloning and transgene functional validation showed that overexpression of Lbr-mir172a promoted a phase change, while overexpression of LbrTOE3 inhibited this process. Subcellular localization and transcriptional activation assays indicated that LbrTOE3 was predominantly localized in the nucleus and showed transcriptional activity. In situ hybridization showed that LbrTOE3 expression was significantly downregulated after alternating temperature treatment. This study elucidates the molecular mechanisms of the phase transition of Lilium and provides a scientific basis for the phase transition in other plants.

Tubby-like proteins (TLPs) transcription factor in different regulatory mechanism in plants: a review

Tubby-like proteins (TLPs) transcription factors are found in single-celled to multi-cellular eukaryotes in the form of large multigene families. TLPs are identified through a specific signature of carboxyl terminal tubby domain, required for plasma membrane tethering and amino terminal F-box domain communicate as functional SCF-type E3 ligases. The comprehensive distribution of TLP gene family members in diverse species indicates some conserved functions of TLPs in multicellular organisms. Plant TLPs have higher gene members than animals and these members reported important role in multiple physiological and developmental processes and various environmental stress responses. Although the TLPs are suggested to be a putative transcription factors but their functional mechanism is not much clear. This review provides significant recent updates on TLP-mediated regulation with an insight into its functional roles, origin and evolution and also phytohormones related regulation to combat with various stresses and its involvement in adaptive stress response in crop plants.

Genome-wide identification and expression analysis of the SPL transcription factor family and its response to abiotic stress in Quinoa (Chenopodium quinoa)

BACKGROUND

Squamous promoter binding protein-like (SPL) proteins are a class of transcription factors that play essential roles in plant growth and development, signal transduction, and responses to biotic and abiotic stresses. The rapid development of whole genome sequencing has enabled the identification and characterization of SPL gene families in many plant species, but to date this has not been performed in quinoa (Chenopodium quinoa).

RESULTS

This study identified 23 SPL genes in quinoa, which were unevenly distributed on 18 quinoa chromosomes. Quinoa SPL genes were then classified into eight subfamilies based on homology to Arabidopsis thaliana SPL genes. We selected three dicotyledonous and monocotyledonous representative species, each associated with C. quinoa, for comparative sympatric mapping to better understand the evolution of the developmental mechanisms of the CqSPL family. Furthermore, we also used 15 representative genes from eight subfamilies to characterize CqSPLs gene expression in different tissues and at different fruit developmental stages under six different abiotic stress conditions.

CONCLUSIONS

This study, the first to identify and characterize SPL genes in quinoa, reported that CqSPL genes, especially CqSPL1, play a critical role in quinoa development and in its response to various abiotic stresses.

Transcription Factor SmSPL2 Inhibits the Accumulation of Salvianolic Acid B and Influences Root Architecture

The SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) transcription factor play vital roles in plant growth and development. Although 15 SPL family genes have been recognized in the model medical plant Salvia miltiorrhiza Bunge, most of them have not been functionally characterized to date. Here, we performed a careful characterization of SmSPL2, which was expressed in almost all tissues of S. miltiorrhiza and had the highest transcriptional level in the calyx. Meanwhile, SmSPL2 has strong transcriptional activation activity and resides in the nucleus. We obtained overexpression lines of SmSPL2 and rSmSPL2 (miR156-resistant SmSPL2). Morphological changes in roots, including longer length, fewer adventitious roots, decreased lateral root density, and increased fresh weight, were observed in all of these transgenic lines. Two rSmSPL2-overexpressed lines were subjected to transcriptome analysis. Overexpression of rSmSPL2 changed root architectures by inhibiting biosynthesis and signal transduction of auxin, while triggering that of cytokinin. The salvianolic acid B (SalB) concentration was significantly decreased in rSmSPL2-overexpressed lines. Further analysis revealed that SmSPL2 binds directly to the promoters of Sm4CL9, SmTAT1, and SmPAL1 and inhibits their expression. In conclusion, SmSPL2 is a potential gene that efficiently manipulate both root architecture and SalB concentration in S. miltiorrhiza.

Genome-wide identification, phylogeny and expression analysis of the SPL gene family and its important role in salt stress in Medicago sativa L

BACKGROUND

SQUAMOSA promoter-binding protein-like (SPL) transcription factors are widely present in plants and are involved in signal transduction, the stress response and development. The SPL gene family has been characterized in several model species, such as A. thaliana and G. max. However, there is no in-depth analysis of the SPL gene family in forage, especially alfalfa (Medicago sativa L.), one of the most important forage crops worldwide.

RESULT

In total, 76 putative MsSPL genes were identified in the alfalfa genome with an uneven distribution. Based on their identity and gene structure, these MsSPLs were divided into eight phylogenetic groups. Seventy-three MsSPL gene pairs arose from segmental duplication events, and the MsSPLs on the four subgenomes of individual chromosomes displayed high collinearity with the corresponding M. truncatula genome. The prediction of the cis-elements in the promoter regions of the MsSPLs detected two copies of ABA (abscisic acid)-responsive elements (ABREs) on average, implying their potential involvement in alfalfa adaptation to adverse environments. The transcriptome sequencing of MsSPLs in roots and leaves revealed that 54 MsSPLs were expressed in both tissues. Upon salt treatment, three MsSPLs (MsSPL17, MsSPL23 and MsSPL36) were significantly regulated, and the transcription level of MsSPL36 in leaves was repressed to 46.6% of the control level.

CONCLUSION

In this study, based on sequence homology, we identified 76 SPL genes in the alfalfa. The SPLs with high identity shared similar gene structures and motifs. In total, 71.1% (54 of 76) of the MsSPLs were expressed in both roots and leaves, and the majority (74.1%) preferred underground tissues to aerial tissues. MsSPL36 in leaves was significantly repressed under salt stress. These findings provide comprehensive information regarding the SPB-box gene family for improve alfalfa tolerance to high salinity.

OsSPLs Regulate Male Fertility in Response to Different Temperatures by Flavonoid Biosynthesis and Tapetum PCD in PTGMS Rice

Photoperiod and thermo-sensitive genic male sterile (PTGMS) rice is an important resource for two line hybrid rice production. The SQUAMOSA–promoter binding, such as the (SPL) gene family, encode the plant specific transcription factors that regulate development and defense responses in plants. However, the reports about SPLs participating in male fertility regulation are limited. Here, we identified 19 OsSPL family members and investigated their involvement in the fertility regulation of the PTGMS rice lines, PA2364S and PA2864S, with different fertility transition temperatures. The results demonstrated that OsSPL2, OsSPL4, OsSPL16 and OsSPL17 affect male fertility in response to temperature changes through the MiR156-SPL module. WGCNA (weighted gene co-expression network analysis) revealed that CHI and APX1 were co-expressed with OsSPL17. Targeted metabolite and flavonoid biosynthetic gene expression analysis revealed that OsSPL17 regulates the expression of flavonoid biosynthesis genes CHI, and the up regulation of flavanones (eriodictvol and naringenin) and flavones (apigenin and luteolin) content contributed to plant fertility. Meanwhile, OsSPL17 negatively regulates APX1 to affect APX (ascorbate peroxidase) activity, thereby regulating ROS (reactive oxygen species) content in the tapetum, controlling the PCD (programmed cell death) process and regulating male fertility in rice. Overall, this report highlights the potential role of OsSPL for the regulation of male fertility in rice and provides a new insight for the further understanding of fertility molecular mechanisms in PTGMS rice.

Conservation and Divergence of SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) Gene Family between Wheat and Rice

The SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE (SPL) gene family affects plant architecture, panicle structure, and grain development, representing key genes for crop improvements. The objective of the present study is to utilize the well characterized SPLs' functions in rice to facilitate the functional genomics of TaSPL genes. To achieve these goals, we combined several approaches, including genome-wide analysis of TaSPLs, comparative genomic analysis, expression profiling, and functional study of TaSPL3 in rice. We established the orthologous relationships of 56 TaSPL genes with the corresponding OsSPLs, laying a foundation for the comparison of known SPL functions between wheat and rice. Some TaSPLs exhibited different spatial-temporal expression patterns when compared to their rice orthologs, thus implicating functional divergence. TaSPL2/6/8/10 were identified to respond to different abiotic stresses through the combination of RNA-seq and qPCR expression analysis. Additionally, ectopic expression of TaSPL3 in rice promotes heading dates, affects leaf and stem development, and leads to smaller panicles and decreased yields per panicle. In conclusion, our work provides useful information toward cataloging of the functions of TaSPLs, emphasized the conservation and divergence between TaSPLs and OsSPLs, and identified the important SPL genes for wheat improvement.

Genome-Wide Characterization of SPL Gene Family in Codonopsis pilosula Reveals the Functions of CpSPL2 and CpSPL10 in Promoting the Accumulation of Secondary Metabolites and Growth of C. pilosula Hairy Root

SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors play critical roles in regulating diverse aspects of plant growth and development, including vegetative phase change, plant architecture, anthocyanin accumulation, lateral root growth, etc. In the present study, 15 SPL genes were identified based on the genome data of Codonopsis pilosula, a well-known medicinal plant. Phylogenetic analysis clustered CpSPLs into eight groups (G1-G8) along with SPLs from Arabidopsis thaliana, Solanum lycopersicum, Oryza sativa and Physcomitrella patens. CpSPLs in the same group share similar gene structure and conserved motif composition. Cis-acting elements responding to light, stress and phytohormone widely exist in their promoter regions. Our qRT-PCR results indicated that 15 CpSPLs were differentially expressed in different tissues (root, stem, leaf, flower and calyx), different developmental periods (1, 2 and 3 months after germination) and various conditions (NaCl, MeJA and ABA treatment). Compared with the control, overexpression of CpSPL2 or CpSPL10 significantly promoted not only the growth of hairy roots, but also the accumulation of total saponins and lobetyolin. Our results established a foundation for further investigation of CpSPLs and provided novel insights into their biological functions. As far as we know, this is the first experimental research on gene function in C. pilosula.

Transcription factor SmSPL7 promotes anthocyanin accumulation and negatively regulates phenolic acid biosynthesis in Salvia miltiorrhiza

Plant-specific SQUAMOSA promoter-binding protein-like (SPL) transcription factors play critical regulatory roles during plant growth and development. However, the functions of SPLs in Salvia miltiorrhiza (SmSPLs; a model medicinal plant) have not been reported. Here, the expression patterns and functions of SmSPL7 were characterized in S. miltiorrhiza. SmSPL7 was expressed in all parts of S. miltiorrhiza, with the highest expression level in the leaves, and could be inhibited by multiple hormones, including methyl jasmonate, auxin, abscisic acid, and gibberellin. SmSPL7 is localized within the nucleus and exhibits robust transcriptional activation activity. Transgenic lines overexpressing SmSPL7 demonstrated pronounced growth inhibition, accompanied by increased anthocyanin accumulation via the genetic activation of the anthocyanin biosynthesis pathway. However, SmSPL7 overexpression significantly decreased salvianolic acid B (SalB) production by inhibiting the transcripts of genes implicated in its biosynthesis pathway. Further analysis indicated that SmSPL7 directly binds to SmTAT1 and Sm4CL9 promoters and blocks their expression to inhibit the biosynthesis of SalB. Taken together, these results indicate that SmSPL7 is a negative regulator of SalB biosynthesis but positively regulates anthocyanin accumulation in S. miltiorrhiza. These findings provide new insights into the functionality of the SPL family while establishing an important foundation for further uncovering the crucial roles of SmSPL7 in the growth of S. miltiorrhiza.

SmSPL6 Induces Phenolic Acid Biosynthesis and Affects Root Development in Salvia miltiorrhiza

Salvia miltiorrhiza is a renowned model medicinal plant species for which 15 SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) family genes have been identified; however, the specific functions of SmSPLs have not been well characterized as of yet. For this study, the expression patterns of SmSPL6 were determined through its responses to treatments of exogenous hormones, including indole acetic acid (IAA), gibberellic acid (GA₃), methyl jasmonic acid (MeJA), and abscisic acid (ABA). To characterize its functionality, we obtained SmSPL6-ovexpressed transgenic S. miltiorrhiza plants and found that overexpressed SmSPL6 promoted the accumulation of phenolic acids and repressed the biosynthesis of anthocyanin. Meanwhile, the root lengths of the SmSPL6-overexpressed lines were significantly longer than the control; however, both the fresh weights and lateral root numbers decreased. Further investigations indicated that SmSPL6 regulated the biosynthesis of phenolic acid by directly binding to the promoter regions of the enzyme genes Sm4CL9 and SmCYP98A14 and activated their expression. We concluded that SmSPL6 regulates not only the biosynthesis of phenolic acids, but also the development of roots in S. miltiorrhiza.

Genome-wide identification of the Tubby-Like Protein (TLPs) family in medicinal model plant Salvia miltiorrhiza

Tubby-Like Proteins (TLPs) are important transcription factors with many functions and are found in both animals and plants. In plants, TLPs are thought to be involved in the abiotic stress response. To reveal the potential function of TLPs in the medicinal model plant Salvia miltiorrhiza, we identified 12 S. miltiorrhiza TLPs (SmTLPs) and conducted a comprehensive analysis. We examined SmTLP gene structure, protein structure, phylogenetics, and expression analysis. Our results show that all SmTLPs, except SmTLP11, have a complete typical Tub domain. Promoter analysis revealed that most SmTLPs are involved in hormone and abiotic stress responses. Expression analysis revealed that the 12 SmTLPs could be divided into three categories: those specifically expressed in roots, those specifically expressed in stems, and those specifically expressed in leaves. Additional studies have shown that SmTLP10 may play an important role in the plant cold resistance, while SmTLP12 may be involved in the S. miltiorrhiza ABA metabolic pathway. Our study represents the first comprehensive investigation of TLPs in S. miltiorrhiza. These data may provide useful clues for future studies and may support the hypotheses regarding the role of TLPs in plant abiotic stress process. All in all, we may provide a reference for improving S. miltiorrhiza quality using genetic engineering technology.

Noncoding RNAs in Medicinal Plants and their Regulatory Roles in Bioactive Compound Production

BACKGROUND

Noncoding RNAs (ncRNAs), such as microRNAs (miRNAs), small interfering RNAs (siRNAs) and long noncoding RNAs (lncRNAs), play significant regulatory roles in plant development and secondary metabolism and are involved in plant response to biotic and abiotic stresses. They have been intensively studied in model systems and crops for approximately two decades and massive amount of information have been obtained. However, for medicinal plants, ncRNAs, particularly their regulatory roles in bioactive compound biosynthesis, are just emerging as a hot research field.

OBJECTIVE

This review aims to summarize current knowledge on herbal ncRNAs and their regulatory roles in bioactive compound production.

RESULTS

So far, scientists have identified thousands of miRNA candidates from over 50 medicinal plant species and 11794 lncRNAs from Salvia miltiorrhiza, Panax ginseng, and Digitalis purpurea. Among them, more than 30 miRNAs and five lncRNAs have been predicted to regulate bioactive compound production.

CONCLUSION

The regulation may achieve through various regulatory modules and pathways, such as the miR397-LAC module, the miR12112-PPO module, the miR156-SPL module, the miR828-MYB module, the miR858-MYB module, and other siRNA and lncRNA regulatory pathways. Further functional analysis of herbal ncRNAs will provide useful information for quality and quantity improvement of medicinal plants.

Genome-wide identification and expression analysis of the trehalose-6-phosphate synthase (TPS) gene family in cucumber (Cucumis sativus L.)

Trehalose-6-phosphate synthase (TPS) is significant in the growth, development and stress resistance of plants. We identified the cucumber TPS family and its physicochemical properties, domains, gene structures, evolutionary relationships, gene locations, cis-acting elements, conserved motifs, and expression patterns using bioinformatics. Our results uncovered seven CsTPS genes in the cucumber genome and named CsTPS1-CsTPS7 according to their locations in the chromosomes. Seven CsTPS genes were randomly distributed in six cucumber chromosomes. Domain analysis showed that the TPS and TPP domains exist in all CsTPSs, and an additional hydrolase-3 domain exist in CsTPS3, CsTPS5 and CsTPS6. Phylogenetic analysis showed that TPS proteins from Arabidopsis, rice, soybean, and cucumber were divided into two subfamilies (Class I and Class II) and they were further divided into seven subgroups. TPS proteins from Arabidopsis and cucumber were grouped together, suggesting a close evolutionary relationship. Gene structure analysis indicated that most Class I genes contained 16-17 introns, while Class II genes (except CsTPS7) had two introns. Motif analysis showed that Class II genes had 10 complete conserved motifs, while Class I genes lacked motif 8 and motif 9. Furthermore, CsTPS genes possessed numerous cis-acting elements related to stress, hormone, and light response in the promoter regions. GO analysis indicated multiple functions for the CsTPS proteins. Expression analysis of CsTPS genes in different tissues found that they were expressed in roots, stems and leaves, with the highest expression levels in roots. The expression analysis of CsTPSs under different treatments showed that CsTPS genes may participate in the response to abiotic stress, plant hormones and sugar treatments.

Genome-wide identification and functional characterization of natural antisense transcripts in Salvia miltiorrhiza

Salvia miltiorrhiza is one of the most widely used traditional medicines. Natural antisense transcripts (NATs) are a class of long noncoding RNAs that can regulate gene expression. Here, we identified 812 NATs, including 168 cis-NATs and 644 trans-NATs from twelve root, flower, and leaf samples of S. miltiorrhiza using RNA-seq. The expression profiles for 41 of 50 NATs and their sense transcripts (STs) obtained from RNA-Seq were validated using qRT-PCR. The expression profiles of 17 NATs positively correlated with their STs. GO and KEGG pathway analyses mapped the STs for cis-NATs to pathways for biosynthesis of secondary metabolites. We characterized four NATs in detail, including NAT0001, NAT0002, NAT0004, and NAT00023. Their STs are kaurene synthase-like 1 and the homologs of UDP-glucose flavonoid 3-O-glucosyltransferase 6, UDP-glycosyltransferase 90A1, and beta-glucosidase 40, respectively. The first gene is involved in the biosynthesis of bioactive tanshinones, the next two are involved in anthocyanin biosynthesis, whereas the last is involved in phenylpropanoid biosynthesis. Besides, we found seven STs that are potential targets of miRNAs. And we found two miRNAs including miR156a and miR7208, might originate from NATs, NAT0112 and NAT0086. The results suggest that S. miltiorrhiza NATs might interact with STs, produce miRNAs, and be regulated by miRNAs. They potentially play significant regulatory roles in the biosynthesis of bioactive compounds.

Protective effects of medicinal plant against diabetes induced cardiac disorder: A review

ETHNOPHARMACOLOGY RELEVANCE

Nowadays, there is an increase in global tendency to use medicinal plants as preventive and therapeutic agents to manage diabetes and its long-term complications such as cardiovascular disorders owing to their availability and valuable traditional background.

AIM OF STUDY

This review aims to introduce common medicinal plants, which have been demonstrated to have cardioprotective effects on diabetes and their mechanisms of action.

MATERIALS AND METHODS

Online literature databases, including Web of Sciences, PubMed, Science Direct, Scopus and Google Scholar were searched without date limitation by May 2020. The following keywords (natural products or medicinal plants or herbal medicine or herb or extract) and (diabetes or antidiabetic or hyperglycemic) and (cardiomyopathy or heart or cardioprotective or cardiac or cardio) were used, and after excluding non-relevant articles, 81 original English articles were selected.

RESULTS

The surveyed medicinal plants induced cardioprotective effects mostly through increasing antioxidant effects leading to attenuating ROS production as well as by inhibiting inflammatory signaling pathways and related cytokines. Moreover, they ameliorated the Na+/K + ATPase pump, the L-type Ca₂⁺ channel current, and the intracellular ATP. They also reduced cardiac remodeling and myocardial cell apoptosis through degradation of caspase-3, Bax, P53 protein, enhancement of Bcl-2 protein expression as well as downregulation of TGFβ1 and TNFα expression. In addition, the extracts improved cardiac function through increasing EF% and FS% as well as restoring hemodynamic parameters.

CONCLUSIONS

The reviewed medicinal plants demonstrated cardioprotective manifestations in diabetes through intervention with mechanisms involved in the diabetic heart to restore cardiovascular complications.

CaSBP11 Participates in the Defense Response of Pepper to Phytophthora capsici through Regulating the Expression of Defense-Related Genes

Squamosa promoter binding protein (SBP)-box genes are plant-specific transcription factors involved in plant growth and development, morphogenesis and biotic and abiotic stress responses. However, these genes have been understudied in pepper, especially with respect to defense responses to Phytophthora capsici infection. CaSBP11 is a SBP-box family gene in pepper that was identified in our previous research. Silencing CaSBP11 enhanced the defense response of pepper plants to Phytophthora capsici. Without treatment, the expression of defense-related genes (CaBPR1, CaPO1, CaSAR8.2 and CaDEF1) increased in CaSBP11-silenced plants. However, the expression levels of these genes were inhibited under transient CaSBP11 expression. CaSBP11 overexpression in transgenic Nicotiana benthamiana decreased defense responses, while in Arabidopsis, it induced or inhibited the expression of genes in the salicylic acid and jasmonic acid signaling pathways. CaSBP11 overexpression in sid2-2 mutants induced AtNPR1, AtNPR3, AtNPR4, AtPAD4, AtEDS1, AtEDS5, AtMPK4 and AtNDR1 expression, while AtSARD1 and AtTGA6 expression was inhibited. CaSBP11 overexpression in coi1-21 and coi1-22 mutants, respectively, inhibited AtPDF1.2 expression and induced AtPR1 expression. These results indicate CaSBP11 has a negative regulatory effect on defense responses to Phytophthora capsici. Moreover, it may participate in the defense response of pepper to Phytophthora capsici by regulating defense-related genes and the salicylic and jasmonic acid-mediated disease resistance signaling pathways.

Genome-Wide Analysis of the Heat Shock Transcription Factor Gene Family in Brassica juncea: Structure, Evolution, and Expression Profiles

Heat shock transcription factor (HSF) is ubiquitous in the whole biological world and plays an important role in regulating growth and development and responses to environment stress. In this study, a total of 60 HSF transcription factors in Brassica juncea genome were identified and analyzed. Phylogenetic analysis showed that HSF genes were divided into three groups namely: A, B, and C, of which group A was further divided into nine subgroups (A1-A9). The analysis of gene structure and conserved motifs showed that some homologous genes are highly conserved. There was strong conservative microcollinearity among Brassica rapa, B. juncea, and Brassica oleracea, which provides a basis for studying the replication of gene families. Moreover, the results revealed that the promoter regions of BjuHSF genes were rich in cis-elements related to growth and development, hormone signal, and stress response. The prediction of protein interaction results showed that HSFs could interact with multiple transcription factors and proteins in the genome, while functional annotation revealed that BjuHSF genes were involved in many biological processes. The expression patterns of BjuHSF genes were analyzed by qPCR, and the results showed that these genes were closely linked to stress response, hormones, and development process. These results are a foundation for further analysis of the regulation mechanism of HSF gene family.

Genome-wide identification, phylogeny and expression analysis of the SPL gene family in wheat

BACKGROUND

Members of the plant-specific SPL gene family (squamosa promoter-binding protein -like) contain the SBP conserved domain and are involved in the regulation of plant growth and development, including the development of plant flowers and plant epidermal hair, the plant stress response, and the synthesis of secondary metabolites. This family has been identified in various plants. However, there is no systematic analysis of the SPL gene family at the genome-wide level of wheat.

RESULTS

In this study, 56 putative TaSPL genes were identified using the comparative genomics method; we renamed them TaSPL001 - TaSPL056 on their chromosomal distribution. According to the un-rooted neighbor joining phylogenetic tree, gene structure and motif analyses, the 56 TaSPL genes were divided into 8 subgroups. A total of 81 TaSPL gene pairs were designated as arising from duplication events and 64 interacting protein branches were identified as involve in the protein interaction network. The expression patterns of 21 randomly selected TaSPL genes in different tissues (roots, stems, leaves and inflorescence) and under 4 treatments (abscisic acid, gibberellin, drought and salt) were detected by quantitative real-time polymerase chain reaction (qRT-PCR).

CONCLUSIONS

The wheat genome contains 56 TaSPL genes and those in same subfamily share similar gene structure and motifs. TaSPL gene expansion occurred through segmental duplication events. Combining the results of transcriptional and qRT-PCR analyses, most of these TaSPL genes were found to regulate inflorescence and spike development. Additionally, we found that 13 TaSPLs were upregulated by abscisic acid, indicating that TaSPL genes play a positive role in the abscisic acid-mediated pathway of the seedling stage. This study provides comprehensive information on the SPL gene family of wheat and lays a solid foundation for elucidating the biological functions of TaSPLs and improvement of wheat yield.

TaSPL13 regulates inflorescence architecture and development in transgenic wheat (Triticum aestivum L.)

The SQUAMOSA promoter-binding protein-like (SPL) proteins play vital roles in plant growth and development in rice (Oryza sative L.) and Arabidopsis thaliana (L.) Heynh. However, few studies regarding the SPL proteins have been reported in wheat. In this study, 56 TaSPLs were clustered into eight groups according to an OsSPL phylogenetic comparison analysis. The expression patterns of TaSPLs in different tissues were analysed by RNA-seq data, and partial results were confirmed by qRT-PCR. Based on the above results, genes such as TaSPL13 and TaSPL15 may be involved in spike or seed development in wheat. Multiple genes that regulate the inflorescence architecture of rice have been identified. Additionally, studies on the genes associated with spikelet development in wheat have been reported relatively rarely. Here, TaSPL13-2B was transferred into wheat cv. Bobwhite. Compared with the wild type, the transgenic lines showed significant increases in the number of florets and grains per spike, indicating that TaSPL13-2B could influence the floret development of wheat. TaSPL13-2B was transferred into rice cv. Nipponbare, which demonstrated that TaSPL13-2B can modify panicle architecture in transgenic rice, with significant increases in panicle length, the number and length of primary branches, and the number of secondary branches.

Genome-wide characterization of the SPL gene family involved in the age development of Jatropha curcas

BACKGROUND

SPL (SQUAMOSA-promoter binding protein-like) proteins form a large family of plant-specific transcription factors that play essential roles in various aspects of plant growth and development. They are potentially important candidates for genetic improvement of agronomic traits. However, there were limited information about the SPL genes in Jatropha curcas, an important biofuel plant.

RESULTS

In Jatropha, 15 JcSPL genes were identified. Phylogenetic analysis revealed that most of the JcSPLs were closely related to SPLs from woody plant rather than herbaceous plant and distantly related to monocotyledon SPLs. Gene structure, conserved motif and repetitive sequence analysis indicated diverse and specific functions of some JcSPL genes. By combination of target prediction and degradome sequencing analysis, 10 of the 15 JcSPLs were shown to be targets of JcmiR156. Quantitative PCR analysis showed diversified spatial-temporal expression patterns of JcSPLs. It is interesting that the expression levels of JcSPL3 were the highest in all tissues examined in 7- or 10-year-old plants and exhibited increasing trend with plant age, suggesting its important role in the regulation of age development in Jatropha. Overexpression of JcSPL3 in Arabidopsis resulted in earlier flowering time, shorter silique length and reduced biomass of roots.

CONCLUSIONS

Through comprehensive and systematic analysis of phylogenetic relationships, conserved motifs, gene structures, chromosomal locations, repetitive sequence and expression patterns, 15 JcSPL genes were identified in Jatropha and characterized in great detail. These results provide deep insight into the evolutionary origin and biological significance of plant SPLs and lay the foundation for further functional characterization of JcSPLs with the purpose of genetic improvement in Jatropha.

Selection of suitable reference genes for qRT-PCR expression analysis of Codonopsis pilosula under different experimental conditions

Codonopsis pilosula is a well-known medicinal plant. Although its transcriptome sequence has been published, suitable reference genes have not been systematically identified for conducting expression analyses via quantitative real-time polymerase chain reaction (qRT-PCR). To screen appropriate genes for use with this species, we applied four different methods-GeNorm, NormFinder, BestKeeper, and RefFinder-to evaluate the stability of 13 candidates: CpiEF1Bb, CpiCACS, CpiF-Box, Cpiβ-Tubulin, CpiGAPDH, CpiActin2, CpiAPT1, CpiActin7, CpiActin8, CpiRPL6, CpiHAF1, CpiTubulin6, and CpiUBQ12. Expression was examined by qRT-PCR for various tissue types, chemical treatments, and developmental stages. For all tested samples, CpiGAPDH proved to be the most stable. Comprehensive analysis indicated that the most stable internal reference genes were CpiF-Box and CpiCACS in different tissues and at different developmental stages, respectively. Under NaCl stress, CpiAPT1 was the best internal reference gene. For methyl jasmonate and abscisic acid treatments, CpiGAPDH and CpiF-Box, respectively, presented the highest degree of expression stability. Based on these findings, we chose CpiSPL9 as the target gene for validating the suitability of these selected reference genes. All of these results provide a foundation for accurate quantification of expression levels by genes of interest in C. pilosula.

Integrated Analysis of mRNA and microRNA Elucidates the Regulation of Glycyrrhizic Acid Biosynthesis in Glycyrrhiza uralensis Fisch

Licorice (Glycyrrhiza) is a staple Chinese herbal medicine in which the primary bioactive compound is glycyrrhizic acid (GA), which has important pharmacological functions. To date, the structural genes involved in GA biosynthesis have been identified. However, the regulation of these genes in G. uralensis has not been elucidated. In this study, we performed a comprehensive analysis based on the transcriptome and small RNAome by high-throughput sequencing. In total, we identified 18 structural GA genes and 3924 transporter genes. We identified genes encoding 2374 transporters, 1040 transcription factors (TFs), 262 transcriptional regulators (TRs) and 689 protein kinases (PKs), which were coexpressed with at least one structural gene. We also identified 50,970 alternative splicing (AS) events, in which 17 structural genes exhibited AS. Finally, we also determined that miRNAs potentially targeted 4 structural genes, and 318, 8, and 218 miRNAs potentially regulated 150 TFs, 34 TRs, and 88 PKs, respectively, related to GA. Overall, the results of this study helped to elucidate the gene expression and regulation of GA biosynthesis in G. uralensis, provided a theoretical basis for the synthesis of GA via synthetic biology, and laid a foundation for the cultivation of new varieties of licorice with high GA content.

Genome-wide identification and expression analysis of the superoxide dismutase (SOD) gene family in Salvia miltiorrhiza

Adverse environmental conditions, such as salinity, cold, drought, heavy metals, and pathogens affect the yield and quality of Salvia miltiorrhiza, a well-known medicinal plant used for the treatment of cardiovascular and cerebrovascular diseases. Superoxide dismutase (SOD), a key enzyme of antioxidant system in plants, plays a vital role in protecting plants against various biotic and abiotic stresses via scavenging the reactive oxygen species produced by organisms. However, little is known about the SOD gene family in S. miltiorrhiza. In this study, eight SOD genes, including three Cu/Zn-SODs, two Fe-SODs and three Mn-SODs, were identified in the S. miltiorrhiza genome. Their gene structures, promoters, protein features, phylogenetic relationships, and expression profiles were comprehensively investigated. Gene structure analysis implied that most SmSODs have different introns/exons distrbution patterns. Many cis-elements related to different stress responses or plant hormones were found in the promoter of each SmSOD. Expression profile analysis indicated that SmSODs exhibited diverse responses to cold, salt, drought, heavy metal, and plant hormones. Additionally, 31 types of TFs regulating SmSODs were predicted and analyzed. These findings provided valuable information for further researches on the functions and applications of SmSODs in S. miltiorrhiza growth and adaptation to stress.

The Role of EjSPL3, EjSPL4, EjSPL5, and EjSPL9 in Regulating Flowering in Loquat (Eriobotrya japonica Lindl.)

The age pathway is important for regulating flower bud initiation in flowering plants. The major regulators in this pathway are miR156 and SPL transcription factors. To date, SPL genes have been identified in many species of plants. Loquat, as a woody fruit tree of Rosaceae, is unique in flowering time as it blooms in winter. However, the study of its SPL homologous genes on the regulation mechanism of flowering time is still limited. In this study, four SPL homologs—EjSPL3, EjSPL4, EjSPL5, and EjSPL9—are cloned from loquat, and phylogenetic analysis showed that they share a high sequence similarity with the homologues from other plants, including a highly conserved SQUAMOSA promoter binding protein (SBP)-box domain. EjSPL3, EjSPL4, EjSPL5 are localized in the cytoplasm and nucleus, and EjSPL9 is localized only in the nucleus. EjSPL4, EjSPL5, and EjSPL9 can significantly activate the promoters of EjSOC1-1, EjLFY-1, and EjAP1-1; overexpression of EjSPL3, EjSPL4, EjSPL5, and EjSPL9 in wild-type Arabidopsis thaliana can promote flowering obviously, and downstream flowering genes expression were upregulated. Our work indicated that the EjSPL3, EjSPL4, EjSPL5, and EjSPL9 transcription factors are speculated to likely participate in flower bud differentiation and other developmental processes in loquat. These findings are helpful to analyze the flowering regulation mechanism of loquat and provide reference for the study of the flowering mechanism of other woody fruit trees.

Genome-wide identification of the SPL gene family in Tartary Buckwheat (Fagopyrum tataricum) and expression analysis during fruit development stages

BACKGROUND

SPL (SQUAMOSA promoter binding protein-like) is a class of plant-specific transcription factors that play important roles in many growth and developmental processes, including shoot and inflorescence branching, embryonic development, signal transduction, leaf initiation, phase transition, and flower and fruit development. The SPL gene family has been identified and characterized in many species but has not been well studied in tartary buckwheat, which is an important edible and medicinal crop.

RESULTS

In this study, 24 Fagopyrum tataricum SPL (FtSPL) genes were identified and renamed according to the chromosomal distribution of the FtSPL genes. According to the amino acid sequence of the SBP domain and gene structure, the SPL genes were divided into eight groups (group I to group VII) by phylogenetic tree analysis. A total of 10 motifs were detected in the tartary buckwheat SPL genes. The expression patterns of 23 SPL genes in different tissues and fruits at different developmental stages (green fruit stage, discoloration stage and initial maturity stage) were determined by quantitative real-time polymerase chain reaction (qRT-PCR).

CONCLUSIONS

The tartary buckwheat genome contained 24 SPL genes, and most of the genes were expressed in different tissues. qRT-PCR showed that FtSPLs played important roles in the growth and development of tartary buckwheat, and genes that might regulate flower and fruit development were preliminarily identified. This work provides a comprehensive understanding of the SBP-box gene family in tartary buckwheat and lays a significant foundation for further studies on the functional characteristics of FtSPL genes and improvement of tartary buckwheat crops.

Genome-wide identification of the SPL gene family in Dichanthelium oligosanthes

SQUAMOSA promoter-binding protein-like (SPL) transcription factors play vital roles in various plant physiological processes. Although, the identification of the SPL gene family has been done in C4 grass plants, including rice and maize, the same has not been characterized in the C3 grass species Dichanthelium oligosanthes. In this study, 14 SPL genes were identified in the genome of D. oligosanthes. Gene structure analysis of the identified DoSPLs revealed the similarity and redundancy in their exon/intron organizations. Sequence comparisons within the DoSPLs and along with rice SPLs revealed the putative paralogs and orthologs in D. oligosanthes SPL genes. Phylogenetic analysis clustered the DoSPLs into eight groups along with other plant SPLs. Identification of the conserved SBP motifs in all 14 DoSPLs suggested them to be putative SPLs. In addition, the prediction of sub-cellular localization and associated functions for DoSPLs further supported to be SPL genes. The outcome of this study can serve as a framework for the isolation and functional validation of SPL genes in D. oligosanthes.

The SPB-Box Transcription Factor AaSPL2 Positively Regulates Artemisinin Biosynthesis in Artemisia annua L

Artemisinin, an important compound produced by Artemisia annua, is the active ingredient in the treatment of malaria. Jasmonic acid, one of the phytohormones, is an important elicitor of artemisinin biosynthesis by enhancing transcription levels of transcription factors. SPL transcription factors are plant-specific transcription factors of plant growth, development, and secondary metabolism regulation. However, to date, the SPL transcription factors that regulate artemisinin biosynthesis is currently unclear. Here, we show that an SPL transcription factor can positively regulate artemisinin biosynthesis by binding to the promoter of artemisinin biosynthetic pathway genes. We screened AaSPL2 by gene expression profiles analysis in 14 SPL transcription factors. We demonstrated that AaSPL2 can activate the promoter of DBR2 by dual-LUC assy. Moreover, in the AaSPL2 overexpression plants, the artemisinin content was increased by 33-86%, and in the AaSPL2 -RNAi transgenic plants, artemisinin content was decreased by 33-65%. These data suggest that AaSPL2 and DBR2 interact with a "GTAC" cis-element in the DBR2 promoter, mediating the transcriptional activation of DBR2 in response to JA and resulting in the improvement on artemisinin content.

Heterologous Expression of Salvia miltiorrhiza MicroRNA408 Enhances Tolerance to Salt Stress in Nicotiana benthamiana

MicroRNAs (miRNAs) are a class of endogenous small RNAs that regulate the expression of target genes post-transcriptionally; they are known to play major roles in development and responses to abiotic stress. MicroRNA408 (miR408) is a conserved small RNA in plants; it was reported that miR408 genes were involved in abiotic stress in Arabidopsis. However, miR408 in Salvia miltiorrhiza has been rarely investigated. In this study, we cloned Sm-MIR408, the miR408 precursor sequence, and its promoter sequence from S. miltiorrhiza and the role in tolerance to salt stress is described. The effects of salt stress on miR408 expression were studied by using β-glucuronidase (GUS) staining. Our data indicated that transgenic tobacco overexpressing Sm-MIR408 promoted seed germination and reduced the accumulation of reactive oxygen species under salt stress. Transcript levels of antioxidative genes, i.e., NbSOD, NbPOD, and NbCAT, and their enzyme activities increased in salinity-stressed transgenic tobacco plants, suggesting a better antioxidant system to cope the oxidative damage caused by salinity stress. Taken together, these findings indicated that miR408 functions in positive responses to salt tolerance in tobacco.

Genome-wide identification and expression analysis of the SPL gene family in woodland strawberry Fragaria vesca

SQUAMOSA promoter-binding protein-like (SPL) is a class of plant-specific transcription factors that play critical roles in regulating plant growth and development. However, little systematic research on SPL genes has been conducted in strawberry. In this study, 14 SPL genes were identified in the genome of woodland strawberry (Fragaria vesca), one of the model plants of the family Rosaceae. Chromosome localization analysis indicated that the 14 FvSPL genes were unevenly distributed on six chromosomes. Phylogenetic analysis indicated that the FvSPL proteins could be clustered into six groups (G1 to G6). Genes with similar structure were classified into the same group, implying their functional redundancy. In addition, nine out of the 14 FvSPL genes, belonging to G1, G2, and G5, were found to be the putative targets of FvmiR156 genes. Expression analysis indicated FvSPL genes exhibited highly diverse expression patterns in the tissues and organs examined. The transcript levels of most FvmiR156-targeted FvSPL genes in fruit were lower than those non-miR156-targeted genes. In addition, the expression of the FvmiR156-targeted FvSPL genes decreased during fruit ripening, whereas the expression of FvmiR156 genes increased in fruit during this process. The results provide a foundation for future functional analysis of FvSPL genes in strawberry growth and development.

Systematic analysis of DEMETER-like DNA glycosylase genes shows lineage-specific Smi-miR7972 involved in SmDML1 regulation in Salvia miltiorrhiza

DEMETER-like DNA glycosylases (DMLs) initiate the base excision repair-dependent DNA demethylation to regulate a wide range of biological processes in plants. Six putative SmDML genes, termed SmDML1-SmDML6, were identified from the genome of S. miltiorrhiza, an emerging model plant for Traditional Chinese Medicine (TCM) studies. Integrated analysis of gene structures, sequence features, conserved domains and motifs, phylogenetic analysis and differential expression showed the conservation and divergence of SmDMLs. SmDML1, SmDML2 and SmDML4 were significantly down-regulated by the treatment of 5Aza-dC, a general DNA methylation inhibitor, suggesting involvement of SmDMLs in genome DNA methylation change. SmDML1 was predicted and experimentally validated to be target of Smi-miR7972. Computational analysis of forty whole genome sequences and almost all of RNA-seq data from Lamiids revealed that MIR7972s were only distributed in some plants of the three orders, including Lamiales, Solanales and Boraginales, and the number of MIR7972 genes varied among species. It suggests that MIR7972 genes underwent expansion and loss during the evolution of some Lamiids species. Phylogenetic analysis of MIR7972s showed closer evolutionary relationships between MIR7972s in Boraginales and Solanales in comparison with Lamiales. These results provide a valuable resource for elucidating DNA demethylation mechanism in S. miltiorrhiza.

Identification and characterization of the cytosine-5 DNA methyltransferase gene family in Salvia miltiorrhiza

Cytosine DNA methylation is highly conserved epigenetic modification involved in a wide range of biological processes in eukaryotes. It was established and maintained by cytosine-5 DNA methyltransferases (C5-MTases) in plants. Through genome-wide identification, eight putative SmC5-MTase genes were identified from the genome of Salvia miltiorrhiza, a well-known traditional Chinese medicine material and an emerging model medicinal plant. Based on conserved domains and phylogenetic analysis, eight SmC5-MTase genes were divided into four subfamilies, including MET, CMT, DRM and DNMT2. Genome-wide comparative analysis of the C5-MTase gene family in S. miltiorrhiza and Arabidopsis thaliana, including gene structure, sequence features, sequence alignment and conserved motifs, was carried out. The results showed conservation and divergence of the members of each subfamily in plants. The length of SmC5-MTase open reading frames ranges widely from 1,152 (SmDNMT2) to 5,034 bp (SmMET1). The intron number of SmC5-MTases varies between 7 (SmDRM1) and 20 (SmCMT1 and SmCMT2b). These features were similar to their counterparts from Arabidopsis. Sequence alignment and conserved motif analysis showed the existence of highly conserved and subfamily-specific motifs in the C5-MTases analyzed. Differential transcript abundance was detected for SmC5-MTases, implying genome-wide variance of DNA methylation in different organs and tissues. Transcriptome-wide analysis showed that the transcript levels of all SmC5-MTase genes was slightly changed under yeast extract and methyl jasmonate treatments. Six SmC5-MTases, including SmMET1, SmCMT1, SmCMT2a, SmCMT2b, SmCMT3 and SmDRM1, were salicylic acid-responsive, suggesting the involvement of SmC5-MTases in salicylic acid-dependent immunity. These results provide useful information for demonstrating the role of DNA methylation in bioactive compound biosynthesis and Dao-di herb formation in medicinal plants.

Genomic survey of bZIP transcription factor genes related to tanshinone biosynthesis in Salvia miltiorrhiza

Tanshinones are a class of bioactive components in the traditional Chinese medicine Salvia miltiorrhiza, and their biosynthesis and regulation have been widely studied. Current studies show that basic leucine zipper (bZIP) proteins regulate plant secondary metabolism, growth and developmental processes. However, the bZIP transcription factors involved in tanshinone biosynthesis are unknown. Here, we conducted the first genome-wide survey of the bZIP gene family and analyzed the phylogeny, gene structure, additional conserved motifs and alternative splicing events in S. miltiorrhiza. A total of 70 SmbZIP transcription factors were identified and categorized into 11 subgroups based on their phylogenetic relationships with those in Arabidopsis. Moreover, seventeen SmbZIP genes underwent alternative splicing events. According to the transcriptomic data, the SmbZIP genes that were highly expressed in the Danshen root and periderm were selected. Based on the prediction of bZIP binding sites in the promoters and the co-expression analysis and co-induction patterns in response to Ag⁺ treatment via quantitative real-time polymerase chain reaction (qRT-PCR), we concluded that SmbZIP7 and SmbZIP20 potentially participate in the regulation of tanshinone biosynthesis. These results provide a foundation for further functional characterization of the candidate SmbZIP genes, which have the potential to increase tanshinone production.

Genome-wide identification and characterization of SPL transcription factor family and their evolution and expression profiling analysis in cotton

Plant specific transcription factors, SQUAMOSA promoter-binding protein-like (SPL), are involved in many biological processes. However, no systematical study has been reported in cotton. In this study, a total of 177 SPL genes were identified, including 29, 30, 59 and 59 SPLs in Gossypium arboreum, G. raimondii, G. barbadense, and G. hirsutum, respectively. These SPL genes were classified into eight phylogenetical groups. The gene structure, conserved motif, and clustering were highly conserved within each orthologs. Two zinc finger-like structures (Cys3His and Cys2HisCys) and NLS segments were existed in all GrSPLs. Segmental duplications play important roles in SPL family expansion, with 20 genes involved in segmental duplications and 2 in tandem duplications, and ten ortholog pairs in syntenic regions between G. raimondii and A. thaliana. Several putative cis-elements, involved in light, stresses and phytohormones response, were found in the promoter regions of GhSPLs, suggesting that plant responses to those environmental changes may be induced through targeting SPL transcription factors. RNA-seq analysis shows that SPL genes were differentially expressed in cotton; some were highly expressed during fiber initiation and early development. Comparing with other plants, SPL genes show subfunctionalization, lost and/or gain functions in cotton during long-term domestication and evolution.

Molecular Characterization of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) Gene Family in Betula luminifera

As a major family of plant-specific transcription factors, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes play vital regulatory roles in plant growth, development and stress responses. In this study, 18 SPL genes were identified and cloned from Betula luminifera. Two zinc finger-like structures and a nuclear location signal (NLS) segments were existed in the SBP domains of all BlSPLs. Phylogenetic analysis showed that these genes were clustered into nine groups (group I-IX). The intron/exon structure and motif composition were highly conserved within the same group. 12 of the 18 BlSPLs were experimentally verified as the targets of miR156, and two cleavage sites were detected in these miR156-targeted BlSPL genes. Many putative cis-elements, associated with light, stresses and phytohormones response, were identified in the promoter regions of BlSPLs, suggesting that BlSPL genes are probably involved in important physiological processes and developmental events. Tissue-specific expression analysis showed that miR156-targeted BlSPLs exhibited a more differential expression pattern, while most miR156-nontargeted BlSPLs tended to be constitutively expressed, suggesting the distinct roles of miR156-targeted and nontargeted BlSPLs in development and growth of B. luminifera. Further expression analysis revealed that miR156-targeted BlSPLs were dramatically up-regulated with age, whereas mature BlmiR156 level was apparently declined with age, indicating that miR156/SPL module plays important roles in vegetative phase change of B. luminifera. Moreover, yeast two-hybrid assay indicated that several miR156-targeted and nontargeted BlSPLs could interact with two DELLA proteins (BlRGA and BlRGL), which suggests that certain BlSPLs take part in the GA regulated processes through protein interaction with DELLA proteins. All these results provide an important basis for further exploring the biological functions of BlSPLs in B. luminifera.

Genome-wide identification and expression analysis of SBP-like transcription factor genes in Moso Bamboo (Phyllostachys edulis)

BACKGROUND

The SQUAMOSA promoter binding protein-like (SPL) proteins are plant-specific transcription factors (TFs) that function in a variety of developmental processes including growth, flower development, and signal transduction. SPL proteins are encoded by a gene family, and these genes have been characterized in two model grass species, Zea mays and Oryza sativa. The SPL gene family has not been well studied in moso bamboo (Phyllostachys edulis), a woody grass species.

RESULTS

We identified 32 putative PeSPL genes in the P. edulis genome. Phylogenetic analysis arranged the PeSPL protein sequences in eight groups. Similarly, phylogenetic analysis of the SBP-like and SBP proteins from rice and maize clustered them into eight groups analogous to those from P. edulis. Furthermore, the deduced PeSPL proteins in each group contained very similar conserved sequence motifs. Our analyses indicate that the PeSPL genes experienced a large-scale duplication event ~15 million years ago (MYA), and that divergence between the PeSPL and OsSPL genes occurred 34 MYA. The stress-response expression profiles and tissue-specificity of the putative PeSPL gene promoter regions showed that SPL genes in moso bamboo have potential biological functions in stress resistance as well as in growth and development. We therefore examined PeSPL gene expression in response to different plant hormone and drought (polyethylene glycol-6000; PEG) treatments to mimic biotic and abiotic stresses. Expression of three (PeSPL10, -12, -17), six (PeSPL1, -10, -12, -17, -20, -31), and nine (PeSPL5, -8, -9, -14, -15, -19, -20, -31, -32) genes remained relatively stable after treating with salicylic acid (SA), gibberellic acid (GA), and PEG, respectively, while the expression patterns of other genes changed. In addition, analysis of tissue-specific expression of the moso bamboo SPL genes during development showed differences in their spatiotemporal expression patterns, and many were expressed at high levels in flowers and leaves.

CONCLUSIONS

The PeSPL genes play important roles in plant growth and development, including responses to stresses, and most of the genes are expressed in different tissues. Our study provides a comprehensive understanding of the PeSPL gene family and may enable future studies on the function and evolution of SPL genes in moso bamboo.

Genome-wide identification and characterization of the SPL gene family in Ziziphus jujuba

SQUAMOSA Promoter-Binding Protein-Likes (SPLs) are plant specific transcription factors playing important roles in plant growth and development. The SPL gene family has been studied in various plant species; however, there is no report about SPLs in Zizyphus jujuba. In this study, we identified 18 putative ZjSPL genes in Z. jujuba using a genome-wide analysis. Sequence features, gene structures, conserved domains and motifs were analyzed. The phylogenetic relationships of SPLs in Z. jujuba and A. thaliana were revealed. A total of 5 pairs of ZjSPLs were identified, suggesting the importance of gene duplication in SPL gene expansion in Z. jujuba. In addition, 11 of the 18 ZjSPLs, belonging to G1, G2 and G5 subgroups, were found to be targets of miR156, suggesting the conservation of miR156-mediated posttranscriptional regulation in plants. Expression analysis revealed that eight ZjSPL genes were responsive to the infection of witches'-broom phytoplasma. Our results provide a basis for the further elucidation of the biological function of ZjSPLs and their regulation in witches'-broom disease.

Characterization of the polyphenol oxidase gene family reveals a novel microRNA involved in posttranscriptional regulation of PPOs in Salvia miltiorrhiza

Salvia miltiorrhiza is a well-known material of traditional Chinese medicine. Understanding the regulatory mechanisms of phenolic acid biosynthesis and metabolism are important for S. miltiorrhiza quality improvement. We report here that S. miltiorrhiza contains 19 polyphenol oxidases (PPOs), forming the largest PPO gene family in plant species to our knowledge. Analysis of gene structures and sequence features revealed the conservation and divergence of SmPPOs. SmPPOs were differentially expressed in plant tissues and eight of them were predominantly expressed in phloem and xylem, indicating that some SmPPOs are functionally redundant, whereas the others are associated with different physiological processes. Expression patterns of eighteen SmPPOs were significantly altered under MeJA treatment, and twelve were yeast extract and Ag⁺-responsive, suggesting the majority of SmPPOs are stress-responsive. Analysis of high-throughput small RNA sequences and degradome data showed that miR1444-mediated regulation of PPOs existing in P. trichocarpa is absent from S. miltiorrhiza. Instead, a subset of SmPPOs was posttranscriptionally regulated by a novel miRNA, termed Smi-miR12112. It indicates the specificity and significance of miRNA-mediated regulation of PPOs. The results shed light on the regulation of SmPPO expression and suggest the complexity of SmPPO-associated phenolic acid biosynthesis and metabolism.

Identification of Symmetrical RNA Editing Events in the Mitochondria of Salvia miltiorrhiza by Strand-specific RNA Sequencing

Salvia miltiorrhiza is one of the most widely-used medicinal plants. Here, we systematically analyzed the RNA editing events in its mitochondria. We developed a pipeline using REDItools to predict RNA editing events from stand-specific RNA-Seq data. The predictions were validated using reverse transcription, RT-PCR amplification and Sanger sequencing experiments. Putative sequences motifs were characterized. Comparative analyses were carried out between S. miltiorrhiza, Arabidopsis thaliana and Oryza sativa. We discovered 1123 editing sites, including 225 “C to U” sites in the protein-coding regions. Fourteen of sixteen (87.5%) sites were validated. Three putative DNA motifs were identified around the predicted sites. The nucleotides on both strands at 115 of the 225 sites had undergone RNA editing, which we called symmetrical RNA editing (SRE). Four of six these SRE sites (66.7%) were experimentally confirmed. Re-examination of strand-specific RNA-Seq data from A. thaliana and O. sativa identified 327 and 369 SRE sites respectively. 78, 20 and 13 SRE sites were found to be conserved among A. thaliana, O. sativa and S. miltiorrhiza respectively. This study provides a comprehensive picture of RNA editing events in the mitochondrial genome of S. miltiorrhiza. We identified SREs for the first time, which may represent a universal phenomenon.

Computational identification and systematic classification of novel GRAS genes in Isatis indigotica

Isatis indigotica Fort., belonging to Cruciferae, is one of the most commonly used plants in traditional Chinese medicine. The accumulation of the effective components of I. indigotica is related with its growth conditions. The GRAS genes are members of a multigene family of transcriptional regulators that play a crucial role in plant growth. Although the activities of many GRAS genes have long been recognized, only in recent years were some of them identified and functionally characterized in detail. In the present study, 41 GRAS genes were identified from I. indigotica through bioinformatics methods for the first time. They were classified into ten groups according to the classification of Arabidopsis and rice. The characterization, gene structure, conserved motifs, disordered N-terminal domains, and phylogenetic reconstruction of these GRASs were analyzed. Forty-three orthologous gene pairs were shared by I. indigotica and Arabidopsis, and interaction networks of these orthologous genes were constructed. Furthermore, gene expression patterns were investigated by analysis in methyl jasmonate (MeJA)-treated I. indigotica hairy roots based on RNA-seq data. In conclusion, this comprehensive analysis would provide rich resources for further studies of GRAS protein functions in this plant.

Genome-Wide Identification and Analysis of MicroRNAs Involved in Witches'-Broom Phytoplasma Response in Ziziphus jujuba

MicroRNAs (miRNAs) play an important role in responding to biotic and abiotic stresses in plants. Jujube witches'-broom a phytoplasma disease of Ziziphus jujuba is prevalent in China and is a serious problem to the industry. However, the molecular mechanism of the disease is poorly understood. In this study, genome-wide identification and analysis of microRNAs in response to witches'-broom was performed. A total of 85 conserved miRNA unique sequences belonging to 32 miRNA families and 24 novel miRNA unique sequences, including their complementary miRNA* strands were identified from small RNA libraries derived from a uninfected and witches'-broom infected Z. jujuba plant. Differentially expressed miRNAs associated with Jujube witches'-broom disease were investigated between the two libraries, and 12 up-regulated miRNAs and 10 down- regulated miRNAs identified with more than 2 fold changes. Additionally, 40 target genes of 85 conserved miRNAs and 49 target genes of 24 novel miRNAs were predicted and their putative functions assigned. Using the modified 5'-RACE method, we confirmed that SPL and MYB were cleaved by miR156 and miR159, respectively. Our results provide insight into the molecular mechanisms of witches'-broom disease in Z. jujuba.

Genome-wide analysis of auxin response factor gene family members in medicinal model plant Salvia miltiorrhiza

Auxin response factors (ARFs) can function as transcriptional activators or repressors to regulate the expression of auxin response genes by specifically binding to auxin response elements (AuxREs) during plant development. Based on a genome-wide strategy using the medicinal model plant Salvia miltiorrhiza, 25 S. miltiorrhiza ARF (SmARF) gene family members in four classes (class Ia, IIa, IIb and III) were comprehensively analyzed to identify characteristics including gene structures, conserved domains, phylogenetic relationships and expression patterns. In a hybrid analysis of the phylogenetic tree, microRNA targets, and expression patterns of SmARFs in different organs, root tissues, and methyl jasmonate or indole-3-acetic acid treatment conditions, we screened for candidate SmARFs involved in various developmental processes of S. miltiorrhiza. Based on this analysis, we predicted that SmARF25, SmARF7, SmARF16 and SmARF20 are involved in flower, leaf, stem and root development, respectively. With the further insight into the targets of miR160 and miR167, specific SmARF genes in S. miltiorrhiza might encode products that participate in biological processes as described for ARF genes in Arabidopsis. Our results provide a foundation for understanding the molecular basis and regulatory mechanisms of SmARFs in S. miltiorrhiza.

Summary: Genome-wide analysis identified 25 ARF gene members (seven transcriptional activators and 18 repressors) in S. miltiorrhiza. The gene structures, functional domains, miRNA targets and expression patterns were analyzed in detail.

Genome-Wide Identification and Analysis of the SBP-Box Family Genes under Phytophthora capsici Stress in Pepper (Capsicum annuum L.)

SQUAMOSA promoter binding protein (SBP)-box genes encode plant-specific transcription factors that are extensively involved in many physiological and biochemical processes, including growth, development, and signal transduction. However, pepper (Capsicum annuum L.) SBP-box family genes have not been well characterized. We investigated SBP-box family genes in the pepper genome and characterized these genes across both compatible and incompatible strain of Phytophthora capsici, and also under different hormone treatments. The results indicated that total 15 members were identified and distributed on seven chromosomes of pepper. Phylogenetic analysis showed that SBP-box genes of pepper can be classified into six groups. In addition, duplication analysis within pepper genome, as well as between pepper and Arabidopsis genomes demonstrated that there are four pairs of homology of SBP-box genes in the pepper genome and 10 pairs between pepper and Arabidopsis genomes. Tissue-specific expression analysis of the CaSBP genes demonstrated their diverse spatiotemporal expression patterns. The expression profiles were similarly analyzed following exposure to P. capsici inoculation and hormone treatments. It was shown that nine of the CaSBP genes (CaSBP01, 02, 03, 04, 05, 06, 11, 12, and 13) exhibited a dramatic up-regulation after compatible HX-9 strain (P. capsici) inoculation, while CaSBP09 and CaSBP15 were down-regulated. In case of PC strain (P. capsici) infection six of the CaSBP genes (CaSBP02, 05, 06, 11, 12, and 13) were arose while CaSBP14 was down regulated. Furthermore, Salicylic acid, Methyl jasmonate and their biosynthesis inhibitors treatment indicated that some of the CaSBP genes are potentially involved in these hormone regulation pathways. This genome-wide identification, as well as characterization of evolutionary relationships and expression profiles of the pepper CaSBP genes, will help to improve pepper stress tolerance in the future.

Plastoquinone and Ubiquinone in Plants: Biosynthesis, Physiological Function and Metabolic Engineering

Plastoquinone (PQ) and ubiquinone (UQ) are two important prenylquinones, functioning as electron transporters in the electron transport chain of oxygenic photosynthesis and the aerobic respiratory chain, respectively, and play indispensable roles in plant growth and development through participating in the biosynthesis and metabolism of important chemical compounds, acting as antioxidants, being involved in plant response to stress, and regulating gene expression and cell signal transduction. UQ, particularly UQ₁₀, has also been widely used in people's life. It is effective in treating cardiovascular diseases, chronic gingivitis and periodontitis, and shows favorable impact on cancer treatment and human reproductive health. PQ and UQ are made up of an active benzoquinone ring attached to a polyisoprenoid side chain. Biosynthesis of PQ and UQ is very complicated with more than thirty five enzymes involved. Their synthetic pathways can be generally divided into two stages. The first stage leads to the biosynthesis of precursors of benzene quinone ring and prenyl side chain. The benzene quinone ring for UQ is synthesized from tyrosine or phenylalanine, whereas the ring for PQ is derived from tyrosine. The prenyl side chains of PQ and UQ are derived from glyceraldehyde 3-phosphate and pyruvate through the 2-C-methyl-D-erythritol 4-phosphate pathway and/or acetyl-CoA and acetoacetyl-CoA through the mevalonate pathway. The second stage includes the condensation of ring and side chain and subsequent modification. Homogentisate solanesyltransferase, 4-hydroxybenzoate polyprenyl diphosphate transferase and a series of benzene quinone ring modification enzymes are involved in this stage. PQ exists in plants, while UQ widely presents in plants, animals and microbes. Many enzymes and their encoding genes involved in PQ and UQ biosynthesis have been intensively studied recently. Metabolic engineering of UQ₁₀ in plants, such as rice and tobacco, has also been tested. In this review, we summarize and discuss recent research progresses in the biosynthetic pathways of PQ and UQ and enzymes and their encoding genes involved in side chain elongation and in the second stage of PQ and UQ biosynthesis. Physiological functions of PQ and UQ played in plants as well as the practical application and metabolic engineering of PQ and UQ are also included.