An ortholog of LEAFY in Jatropha curcas regulates flowering time and floral organ development

Inhibition of flowering by gibberellins in the woody plant Jatropha curcas is restored by overexpression of JcFT

Jatropha curcas (J. curcas) is a perennial oil-seed plant with vigorous vegetative growth but relatively poor reproductive growth and low seed yield. Gibberellins (GAs) promotes flowering in most annual plants but inhibits flowering in many woody plants, including J. curcas. However, the underlying mechanisms of GA inhibits flowering in perennial woody plants remain unclear. Here, we found that overexpression of the GA biosynthesis gene JcGA20ox1 inhibits flowering in J. curcas and in J. curcas × J. integerrima hybrids. Consistent with this finding, overexpression of the GA catabolic gene JcGA2ox6 promotes flowering in J. curcas. qRTPCR revealed that inhibits floral transition by overexpressing JcGA20ox1 resulted from a decrease in the expression of JcFT and other flowering-related genes, which was restored by overexpressing JcFT in J. curcas. Overexpression of JcGA20ox1 or JcGA2ox6 reduced seed yield, but overexpression of JcFT significantly increased seed yield. Furthermore, hybridization experiments showed that the reduction in seed yield caused by overexpression of JcGA20ox1 or JcGA2ox6 was partially restored by the overexpression of JcFT. In addition, JcGA20ox1, JcGA2ox6 and JcFT were also found to be involved in the regulation of seed oil content and endosperm development. In conclusion, our study revealed that the inhibitory effect of GA on flowering is mediated through JcFT and demonstrated the effects of JcGA20ox1, JcGA2ox6 and JcFT on agronomic traits in J. curcas. This study also indicates the potential value of GA metabolism genes and JcFT in the breeding of new varieties of woody oil-seed plants.

Identification and functional analysis of the LEAFY gene in longan flower induction

BACKGROUND

Flowering at the right time is a very important factor affecting the stable annual yield of longan. However, a lack of knowledge of the regulatory mechanism and key genes of longan flowering restricts healthy development of the longan industry. Therefore, identifying relevant genes and analysing their regulatory mechanism are essential for scientific research and longan industry development.

RESULTS

DlLFY (Dimocarpus longan LEAFY) contains a 1167 bp open reading frame and encodes 388 amino acids. The amino acid sequence has a typical LFY/FLO family domain. DlLFY was expressed in all tissues tested, except for the leaf, pericarp, and pulp, with the highest expression occurring in flower buds. Expression of DlLFY was significantly upregulated at the early flower induction stage in "SX" ("Shixia"). The results of subcellular localization and transactivation analysis showed that DlLFY is a typical transcription factor acting as a transcriptional activator. Moreover, overexpression of DlLFY in Arabidopsis promoted early flowering and restrained growth, resulting in reduced plant height and rosette leaf number and area in transgenic plants. DNA affinity purification sequencing (DAP-Seq) analysis showed that 13 flower-related genes corresponding to five homologous genes of Arabidopsis may have binding sites and be putative target genes. Among these five flower-related genes, only AtTFL1 (terminal flower 1) was strongly inhibited in transgenic lines.

CONCLUSION

Taken together, these results indicate that DlLFY plays a pivotal role in controlling longan flowering, possibly by interacting with TFL1.

An overview of floral regulatory genes in annual and perennial plants

The floral initiation in angiosperms is a complex process influenced by endogenous and exogenous signals. With this approach, we aim to provide a comprehensive review to integrate this complex floral regulatory process and summarize the regulatory genes and their functions in annuals and perennials. Seven primary paths leading to flowering have been discovered in Arabidopsis under several growth condition that include; photoperiod, ambient temperature, vernalization, gibberellins, autonomous, aging and carbohydrates. These pathways involve a series of interlinked signaling pathways that respond to both internal and external signals, such as light, temperature, hormones, and developmental cues, to coordinate the expression of genes that are involved in flower development. Among them, the photoperiodic pathway was the most important and conserved as some of the fundamental loci and mechanisms are shared even by closely related plant species. The activation of floral regulatory genes such as FLC, FT, LFY, and SOC1 that determine floral meristem identity and the transition to the flowering stage result from the merging of these pathways. Recent studies confirmed that alternative splicing, antisense RNA and epigenetic modification play crucial roles by regulating the expression of genes related to blooming. In this review, we documented recent progress in the floral transition time in annuals and perennials, with emphasis on the specific regulatory mechanisms along with the application of various molecular approaches including overexpression studies, RNA interference and Virus-induced flowering. Furthermore, the similarities and differences between annual and perennial flowering will aid significant contributions to the field by elucidating the mechanisms of perennial plant development and floral initiation regulation.

JcSEUSS1 negatively regulates reproductive organ development in perennial woody Jatropha curcas

MAIN CONCLUSION

Overexpression of JcSEUSS1 resulted in late flowering, reduced flower number, wrinkled kernels, and decreased seed yield in Jatopha curcas, while downregulation of JcSEUSS1 increased flower number and seed production. The seed oil of Jatropha curcas is suitable as an ideal alternative for diesel fuel, yet the seed yield of Jatropha is restricted by its small number of female flowers and low seed setting rate. Therefore, it is crucial to identify genes that regulate flowering and seed set, and hence improve seed yield. In this study, overexpression of JcSEUSS1 resulted in late flowering, fewer flowers and fruits, and smaller fruits and seeds, causing reduced seed production and oil content. In contrast, the downregulation of JcSEUSS1 by RNA interference (RNAi) technology caused an increase in the flower number and seed yield. However, the flowering time, seed number per fruit, seed weight, and size exhibited no obvious changes in JcSEUSS1-RNAi plants. Moreover, the fatty acid composition also changed in JcSEUSS1 overexpression and RNAi plants, the percentage of unsaturated fatty acids (FAs) was increased in overexpression plants, and the saturated FAs were increased in RNAi plants. These results indicate that JcSEUSS1 played a negative role in regulating reproductive growth and worked redundantly with other genes in the regulation of flowering time, seed number per fruit, seed weight, and size.

Functional verification of the JmLFY gene associated with the flowering of Juglans mandshurica Maxim

In this study, a pBI121-JmLFY plant expression vector was constructed on the basis of obtaining the full-length sequence of the JmLFY gene from Juglans mandshurica, which was then used for genetic transformation via Agrobacterium inflorescence infection using wild-type Arabidopsis thaliana and lfy mutants as transgenic receptors. Seeds of positive A. thaliana plants with high expression of JmLFY were collected and sowed till the homozygous T3 regeneration plants were obtained. Then the expression of flowering-related genes (AtAP1, AtSOC1, AtFT and AtPI) in T3 generation plants were analyzed and the results showed that JmLFY gene overexpression promoted the expression of flowering-related genes and resulted in earlier flowering in A. thaliana. The A. thaliana plants of JmLFY-transformed and JmLFY-transformed lfy mutants appeared shorter leaves, longer fruit pods, and fewer cauline leaves than those of wild-type and the lfy mutants plants, respectively. In addition, some secondary branches in the transgenic plants converted into inflorescences, which indicated that the overexpression of JmLFY promoted the transition from vegetative growth to reproductive growth, and compensate the phenotypic defects of lfy mutant partially. The results provides a scientific reference for formulating reasonable genetic improvement strategies such as shortening childhood, improving yield and quality, and breeding desirable varieties, which have important guiding significance in production.

The plant specific SHORT INTERNODES/STYLISH (SHI/STY) proteins: Structure and functions

Plant specific SHORT INTERNODES/STYLISH (SHI/STY) protein is a transcription factor involved in the formation and development of early lateral organs in plants. However, research on the SHI/STY protein family is not focused enough. In this article, we review recent studies on SHI/STY genes and explore the evolution and structure of SHI/STY. The biological functions of SHI/STYs are discussed in detail in this review, and the application of each biological function to modern agriculture is discussed. All SHI/STY proteins contain typical conserved RING-like zinc finger domain and IGGH domain. SHI/STYs are involved in the formation and development of lateral root, stem extension, leaf morphogenesis, and root nodule development. They are also involved in the regulation of pistil and stamen development and flowering time. At the same time, the regulation of some GA, JA, and auxin signals also involves these family proteins. For each aspect, unanswered or poorly understood questions were identified to help define future research areas. This review will provide a basis for further functional study of this gene family.

Promotion of natural flowers by JcFT depends on JcLFY in the perennial woody species Jatropha curcas

Production of normal gametes is necessary for flowering plant reproduction, which involves the transition from vegetative to reproductive stage and floral organ development. Such transitions and floral development are modulated by various environmental and endogenous stimuli and controlled by sophisticated regulatory networks. FLOWERING LOCUS T (FT) and LEAFY (LFY) are two key genes that integrate signals from multiple genetic pathways in Arabidopsis. However, the comprehensive functions and relationship between these two genes in trees are poorly understood. In this study, we found that JcFT played a vital role in regulating the flowering transition in the perennial woody species Jatropha curcas. JcLFY also involved in regulating this transition and controlled floral organ development. The non-flowering phenotype of JcFT-RNAi was rescued successfully by overexpression of JcLFY, while the abnormal flowers produced by JcLFY silencing were not recovered by JcFT overexpression via hybridization. These results indicate that JcFT, in which a mutation leads to a nonflowering phenotype, is the central gene of the floral meristem transition and that JcLFY, in which a mutation leads to striking changes in flowering and often sterility, is the central floral and inflorescence development gene. Moreover, our hybridization results suggest that JcLFY acts downstream of JcFT in Jatropha.

An ortholog of the MADS-box gene SEPALLATA3 regulates stamen development in the woody plant Jatropha curcas

Overexpression of JcSEP3 causes defective stamen development in Jatropha curcas, in which brassinosteroid and gibberellin signaling pathways may be involved. SEPALLATAs (SEPs), the class E genes of the ABCE model, are required for floral organ determination. In this study, we investigated the role of the JcSEP3 gene in floral organ development in the woody plant Jatropha curcas. Transgenic Jatropha plants overexpressing JcSEP3 displayed abnormal phenotypes such as deficient anthers and pollen, as well as free stamen filaments, whereas JcSEP3-RNA interference (RNAi) transgenic plants had no obvious phenotypic changes, suggesting that JcSEP3 is redundant with other JcSEP genes in Jatropha. Moreover, we compared the transcriptomes of wild-type plants, JcSEP3-overexpressing, and JcSEP3-RNAi transgenic plants. In the JcSEP3-overexpressing transgenic plants, we discovered 25 upregulated genes involved in anther and pollen development, as well as 12 induced genes in brassinosteroid (BR) and gibberellin (GA) signaling pathways. These results suggest that JcSEP3 directly or indirectly regulates stamen development, concomitant with the regulation of BR and GA signaling pathways. Our findings help to understand the roles of SEP genes in stamen development in perennial woody plants.

Isolation and Functional Characterization of a LEAFY Gene in Mango (Mangifera indica L.)

LEAFY (LFY) plays an important role in the flowering process of plants, controlling flowering time and mediating floral meristem differentiation. Owing to its considerable importance, the mango LFY gene (MiLFY; GenBank accession no. HQ585988) was isolated, and its expression pattern and function were characterized in the present study. The cDNA sequence of MiLFY was 1152 bp, and it encoded a 383 amino acid protein. MiLFY was expressed in all tested tissues and was highly expressed in flowers and buds. Temporal expression analysis showed that MiLFY expression was correlated with floral development stage, and two relative expression peaks were detected in the early stages of floral transition and floral organ differentiation. Moreover, 35S::GFP-MiLFY fusion protein was shown to be localized to the nucleus of cells. Overexpression of MiLFY in Arabidopsis promoted early flowering and the conversion of lateral meristems into terminal flowers. In addition, transgenic plants exhibited obvious morphological changes, such as differences in cauline leaf shape, and the number of lateral branches. When driven by the MiLFY promoter, GFP was highly expressed in leaves, floral organs, stems, and roots, during the flowering period. Exogenous gibberellin (GA3) treatment downregulated MiLFY promoter expression, but paclobutrazol (PPP333) upregulated it. Bimolecular fluorescence complementation (BiFC) assays showed that the MiLFY protein can interact with zinc-finger protein 4 (ZFP4) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (MiSOC1D). Taken together, these results indicate that MiLFY plays a pivotal role in controlling mango flowering, and that it is regulated by gibberellin and paclobutrazol.

Comparative transcriptome analysis of gynoecious and monoecious inflorescences reveals regulators involved in male flower development in the woody perennial plant Jatropha curcas

ABCE model genes along with genes related to GA biosynthesis and auxin signalling may play significant roles in male flower development in Jatropha curcas. Flowering plants exhibit extreme reproductive diversity. Jatropha curcas, a woody plant that is promising for biofuel production, is monoecious. Here, two gynoecious Jatropha mutants (bearing only female flowers) were used to identify key genes involved in male flower development. Using comparative transcriptome analysis, we identified 17 differentially expressed genes (DEGs) involved in floral organ development between monoecious plants and the two gynoecious mutants. Among these DEGs, five floral organ identity genes, Jatropha AGAMOUS, PISTILLATA, SEPALLATA 2-1 (JcSEP2-1), JcSEP2-2, and JcSEP3, were downregulated in ch mutant inflorescences; two gibberellin (GA) biosynthesis genes, Jatropha GA REQUIRING 1 and GIBBERELLIN 3-OXIDASE 1, were downregulated in both the ch and g mutants; and two genes involved in the auxin signalling pathway, Jatropha NGATHA1 and STYLISH1, were downregulated in the ch mutant. Furthermore, four hub genes involved in male flower development, namely Jatropha SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE 1, CRYPTOCHROME 2, SUPPRESSOR OF OVEREXPRESSION OF CO 1 and JAGGED, were identified using weighted gene correlation network analysis. These results suggest that floral organ identity genes and genes involved in GA biosynthesis and auxin signalling may participate in male flower development in Jatropha. This study will contribute to understanding sex differentiation in woody perennial plants.

Prospects for the accelerated improvement of the resilient crop quinoa

Crops tolerant to drought and salt stress may be developed by two approaches. First, major crops may be improved by introducing genes from tolerant plants. For example, many major crops have wild relatives that are more tolerant to drought and high salinity than the cultivated crops, and, once deciphered, the underlying resilience mechanisms could be genetically manipulated to produce crops with improved tolerance. Secondly, some minor (orphan) crops cultivated in marginal areas are already drought and salt tolerant. Improving the agronomic performance of these crops may be an effective way to increase crop and food diversity, and an alternative to engineering tolerance in major crops. Quinoa (Chenopodium quinoa Willd.), a nutritious minor crop that tolerates drought and salinity better than most other crops, is an ideal candidate for both of these approaches. Although quinoa has yet to reach its potential as a fully domesticated crop, breeding efforts to improve the plant have been limited. Molecular and genetic techniques combined with traditional breeding are likely to change this picture. Here we analyse protein-coding sequences in the quinoa genome that are orthologous to domestication genes in established crops. Mutating only a limited number of such genes by targeted mutagenesis appears to be a promising route for accelerating the improvement of quinoa and generating a nutritious high-yielding crop that can meet the future demand for food production in a changing climate.

Ectopic expression of an AGAMOUS homologue gene in Jatropha curcas causes early flowering and heterostylous phenotypes

Jatropha curcasseeds are abundant in biodiesel, and low seed yields are linked to poor quality female flowers, which creates a bottleneck for Jatropha seed utilization. Therefore, identifying the genes associated with flowering is crucial for the genetic enrichment of seed yields. Here, we identified an AGAMOUS homologue gene (JcAG) from J. curcas. We found that reproductive organs had higher JcAG expression than vegetative organs, particularly the carpel. Rosette leaves were small and misshapen in 35S:JcAG transgenic lines in comparison with those in wild-type plants. JcAG overexpression caused an extremely early flowering, delayed perianth and stamen filament development, small flowers, and significantly shorter Arabidopsis plants with little fruit. In the JcAG-overexpressing line, the homeotic transformation of sepals into pistillate organs was observed, and floral meristem and organ identity genes were regulated. This study provides insights into the JcAG's function and benefits to our knowledge of the underlying the genetic mechanisms related to floral sex differentiation in Jatropha.

Multi-omics sequencing provides insight into floral transition in Catalpa bungei. C.A. Mey

BACKGROUND

Floral transition plays an important role in development, and proper time is necessary to improve the value of valuable ornamental trees. The molecular mechanisms of floral transition remain unknown in perennial woody plants. "Bairihua" is a type of C. bungei that can undergo floral transition in the first planting year.

RESULTS

Here, we combined short-read next-generation sequencing (NGS) and single-molecule real-time (SMRT) sequencing to provide a more complete view of transcriptome regulation during floral transition in C. bungei. The circadian rhythm-plant pathway may be the critical pathway during floral transition in early flowering (EF) C. bungei, according to horizontal and vertical analysis in EF and normal flowering (NF) C. bungei. SBP and MIKC-MADS-box were seemingly involved in EF during floral transition. A total of 61 hub genes were associated with floral transition in the MEturquoise model with Weighted Gene Co-expression Network Analysis (WGCNA). The results reveal that ten hub genes had a close connection with the GASA homologue gene (Cbu.gene.18280), and the ten co-expressed genes belong to five flowering-related pathways. Furthermore, our study provides new insights into the complexity and regulation of alternative splicing (AS). The ratio or number of isoforms of some floral transition-related genes is different in different periods or in different sub-genomes.

CONCLUSIONS

Our results will be a useful reference for the study of floral transition in other perennial woody plants. Further molecular investigations are needed to verify our sequencing data.

Molecular Mechanisms of the Floral Biology of Jatropha curcas: Opportunities and Challenges as an Energy Crop

Fossil fuel sources are a limited resource and could eventually be depleted. Biofuels have emerged as a renewable alternative to fossil fuels. Jatropha has grown in significance as a potential bioenergy crop due to its high content of seed oil. However, Jatropha's lack of high-yielding seed genotypes limits its potential use for biofuel production. The main cause of lower seed yield is the low female to male flower ratio (1:25-10), which affects the total amount of seeds produced per plant. Here, we review the genetic factors responsible for floral transitions, floral organ development, and regulated gene products in Jatropha. We also summarize potential gene targets to increase seed production and discuss challenges ahead.

AfLFY, a LEAFY homolog in Argyranthemum frutescens, controls flowering time and leaf development

Flowering is important for plant propagation and survival, and it is also closely related to human life. Identifying the molecular mechanisms underlying flower development is essential for plant improvement and breeding. Flower development is a complex physiological process that is regulated by multiple genes. LFY genes play important roles in the floral meristem transition and act as crucial integrators in regulating the floral gene network. Argyranthemum frutescens is an ornamental species cultivated for floral displays, yet little is known about molecular mechanisms driving its flower development. In this study, the LEAFY gene homologue, AfLFY, was identified and cloned from A. frutescens, and its role and expression patterns were characterized. Two distinct copies of AfLFY were found in the A. frutescens genome and both sequences contained a 1248 bp open reading frame that encoded 415 amino acids. The putative protein sequences have a typical LFY family domain. In addition, AfLFY was expressed at the highest levels in young leaves of the vegetative stage and in the shoot apical bud meristem of the reproductive stage. Phylogenetic analysis showed that AfLFY was most closely related to DFL from Chrysanthemum lavandulifolium. Subcellular localization studies revealed that AfLFY localized to the nucleus. Heterologous expression of AfLFY in transgenic tobacco plants shortened its period of vegetative growth, converted the lateral meristems into terminal flowers and promoted precocious flowering. In addition, transgenic plants exhibited obvious morphological changes in leaf shape. qRT-PCR analysis indicated that the expression levels genes related to flowering, FT, SOC1, and AP1 were significantly upregulated in AfLFY transgenic plants. Our findings suggested that the AfLFY gene plays a vital role in promoting flowering and leaf development in A. frutescens. These results laid a foundation for us to understand the mechanism of AfLFY in regulation flowering, and the results will be helpful in improving A. frutescens through molecular breeding.

Transcriptome and digital gene expression analysis unravels the novel mechanism of early flowering in Angelica sinensis

Angelica sinensis (Oliv.) Diels is a widely used medicinal plant mainly originated in Gansu, China. Angelica sinensis is greatly demanded in the clinical practice of Chinese medicine due to its broad pharmacological activities of hematopoietic and anti-inflammatory properties. But, the percentage of early flowering in Angelica sinensis arrives to 20%~30%, which severely affects its quality and quantity. Here, transcriptome profiling and digital gene expression analysis were applied to study the mechanism of early flowering in Angelica sinensis. A total of 49,183,534 clean reads were obtained and assembled into 68,262 unigenes, and 49,477 unigenes (72.5%) could be annotated to a minimum of one database in the Nr, Nt, Swiss-Pro, GO, COG and KEGG. Taking the above transcriptome data as a reference, digital gene expression result showed that 5,094 genes expression level were significant changed during early flowering. These annotated genes offered much information promoting that the biosynthesis of secondary metabolites pathway, the hormone signal transduction pathway, and the transcription regulation system may be closely related to the early flowering phenomenon of Angelica sinensis. Further expression patterns of key genes contribute to early flowering were analyzed using quantitative real-time PCR. The transcriptome result offered important gene expression information about early flowering in Angelica sinensis.

Ectopic Expression of Jatropha curcas TREHALOSE-6-PHOSPHATE PHOSPHATASE J Causes Late-Flowering and Heterostylous Phenotypes in Arabidopsis but not in Jatropha

Trehalose-6-phosphate (T6P) phosphatase (TPP), a dephosphorylating enzyme, catalyzes the dephosphorylation of T6P, generating trehalose. In Jatropha, we found six members of the TPP family. Five of them JcTPPA, JcTPPC, JcTPPD, JcTPPG, and JcTPPJ are highly expressed in female flowers or male flowers, or both, suggesting that members of the JcTPP family may participate in flower development in Jatropha. The wide expression of JcTPPJ gene in various organs implied its versatile roles and thus was chosen for unraveling its biological functions during developmental process. We constructed an overexpression vector of JcTPPJ cDNA driven by the cauliflower mosaic virus (CaMV) 35S promoter for genetic transformation. Compared with control Arabidopsis plants, 35S:JcTPPJ transgenic Arabidopsis plants presented greater sucrose contents in their inflorescences and displayed late-flowering and heterostylous phenotypes. Exogenous application of sucrose to the inflorescence buds of wild-type Arabidopsis repressed the development of the perianth and filaments, with a phenocopy of the 35S:JcTPPJ transgenic Arabidopsis. These results suggested that the significantly increased sucrose level in the inflorescence caused (or induced) by JcTTPJ overexpression, was responsible for the formation of heterostylous flower phenotype. However, 35S:JcTPPJ transgenic Jatropha displayed no obvious phenotypic changes, implying that JcTPPJ alone may not be sufficient for regulating flower development in Jatropha. Our results are helpful for understanding the function of TPPs, which may regulate flower organ development by manipulating the sucrose status in plants.

Comprehensive analysis of the longan transcriptome reveals distinct regulatory programs during the floral transition

Background

Longan (Dimocarpus longan Lour.) is an important fruit tree in the subtropical regions of Southeast Asia and Australia. Among the factors affecting D. longan fruit yield, the difficulty and instability of blossoming is one of the most challenging issues. Perpetual flowering (PF) is a crucial trait for fruit trees and is directly linked to production potential. Therefore, studying the molecular regulatory mechanism of longan PF traits is crucial for understanding and solving problems related to flowering. In this study, comparative transcriptome analysis was performed using two longan cultivars that display opposite flowering phenotypes during floral induction.

Results

We obtained 853.72 M clean reads comprising 125.08 Gb. After comparing these data with the longan genome, 27,266 known genes and 1913 new genes were detected. Significant differences in gene expression were observed between the two genotypes, with 6150 and 6202 differentially expressed genes (DEGs) for ‘SJ’ and ‘SX’, respectively. The transcriptional landscape of floral transition at the early stage was very different in these two longan genotypes with respect to key hormones, circadian rhythm, sugar metabolism, and transcription factors. Almost all flowering-related DEGs identified are involved in photoperiod and circadian clock pathways, such as CONSTANS-like (COL), two-component response regulator-like (APRRs), gigantea (GI), and early flowering (EFL). In addition, the leafy (LFY) gene, which is the central floral meristem identity gene, may inhibit PF formation in ‘SJ’.

Conclusion

This study provides a platform for understanding the molecular mechanisms responsible for changes between PF and seasonal flowering (SF) longan genotypes and may benefit studies on PF trait mechanisms of evergreen fruit trees.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5461-3) contains supplementary material, which is available to authorized users.

miR172 Regulates both Vegetative and Reproductive Development in the Perennial Woody Plant Jatropha curcas

Jatropha curcas is a promising feedstock for biofuel production because its oil is highly suitable for processing bio-jet fuels and biodiesel. However, Jatropha exhibits a long juvenile stage in subtropical areas. miR172, a conserved small non-protein-coding RNA molecule with 21 nucleotides, regulates a wide range of developmental processes. To date, however, no studies have examined the function of miR172 in Jatropha. There are five miR172 precursors encoding two mature miR172s in Jatropha, which are expressed in all tissues, with the highest expression level in leaves, and the levels are up-regulated with age. Overexpression of JcmiR172a resulted in early flowering, abnormal flowers, and altered leaf morphology in transgenic Arabidopsis and Jatropha. The expression levels of miR172 target genes were down-regulated, and the flower identity genes were up-regulated in the JcmiR172a-overexpressing transgenic plants. Interestingly, we showed that JcmiR172 might be involved in regulation of stem vascular development through manipulating the expression of cellulose and lignin biosynthesis genes. Overexpression of JcmiR172a enhanced xylem development and reduced phloem and pith development. This study helped elucidate the functions of miR172 in perennial plants, a known age-related miRNA involved in the regulation of perennial plant phase change and organ development.

A gene co-expression network model identifies yield-related vicinity networks in Jatropha curcas shoot system

The plant shoot system consists of reproductive organs such as inflorescences, buds and fruits, and the vegetative leaves and stems. In this study, the reproductive part of the Jatropha curcas shoot system, which includes the aerial shoots, shoots bearing the inflorescence and inflorescence were investigated in regard to gene-to-gene interactions underpinning yield-related biological processes. An RNA-seq based sequencing of shoot tissues performed on an Illumina HiSeq. 2500 platform generated 18 transcriptomes. Using the reference genome-based mapping approach, a total of 64 361 genes was identified in all samples and the data was annotated against the non-redundant database by the BLAST2GO Pro. Suite. After removing the outlier genes and samples, a total of 12 734 genes across 17 samples were subjected to gene co-expression network construction using petal, an R library. A gene co-expression network model built with scale-free and small-world properties extracted four vicinity networks (VNs) with putative involvement in yield-related biological processes as follow; heat stress tolerance, floral and shoot meristem differentiation, biosynthesis of chlorophyll molecules and laticifers, cell wall metabolism and epigenetic regulations. Our VNs revealed putative key players that could be adapted in breeding strategies for J. curcas shoot system improvements.

MicroRNA and Transcription Factor: Key Players in Plant Regulatory Network

Recent achievements in plant microRNA (miRNA), a large class of small and non-coding RNAs, are very exciting. A wide array of techniques involving forward genetic, molecular cloning, bioinformatic analysis, and the latest technology, deep sequencing have greatly advanced miRNA discovery. A tiny miRNA sequence has the ability to target single/multiple mRNA targets. Most of the miRNA targets are transcription factors (TFs) which have paramount importance in regulating the plant growth and development. Various families of TFs, which have regulated a range of regulatory networks, may assist plants to grow under normal and stress environmental conditions. This present review focuses on the regulatory relationships between miRNAs and different families of TFs like; NF-Y, MYB, AP2, TCP, WRKY, NAC, GRF, and SPL. For instance NF-Y play important role during drought tolerance and flower development, MYB are involved in signal transduction and biosynthesis of secondary metabolites, AP2 regulate the floral development and nodule formation, TCP direct leaf development and growth hormones signaling. WRKY have known roles in multiple stress tolerances, NAC regulate lateral root formation, GRF are involved in root growth, flower, and seed development, and SPL regulate plant transition from juvenile to adult. We also studied the relation between miRNAs and TFs by consolidating the research findings from different plant species which will help plant scientists in understanding the mechanism of action and interaction between these regulators in the plant growth and development under normal and stress environmental conditions.