Ethylene Signal Transduction Research Articles

Low temperature conditioning alleviates loss of aroma-related esters of ‘Nanguo’ pears by regulation of ethylene signal transduction

The optimum harvest time for ‘Nanguo’ pears lasts for only 20 days. Refrigeration is a common technique used to extend the fruit supply. However, with low-temperature storage, the proper aroma of the pear is lost when it matures during shelf-life at room temperature. In this study, we investigated the ability of low-temperature conditioning (LTC) to regulate aroma esters of ‘Nanguo’ pears, and identified the key genes in the ethylene signal transduction pathway based on RNA-seq analysis. LTC caused higher ethylene production and effectively alleviated the loss of aroma-related esters in ‘Nanguo’ pears during refrigeration and during the subsequent shelf-life at room temperature. Furthermore, the expression levels of PuERS1, PuEIN4, PuEIN2, and PuERF were increased under LTC treatment. Thus, we speculate that the alleviation effect of LTC on fruit aroma esters is closely related to ethylene signal transduction, including up-regulated expression of PuERS1, PuEIN4, PuEIN2, and PuERF.

Long non-coding RNAs of switchgrass (Panicum virgatum L.) in multiple dehydration stresses

BackgroundLong non-coding RNAs (lncRNAs) play important roles in plant growth and stress responses. Studies of lncRNAs in non-model plants are quite limited, especially those investigating multiple dehydration stresses. In this study, we identified novel lncRNAs and analyzed their functions in dehydration stress memory in switchgrass, an excellent biofuel feedstock and soil-conserving plant in the Gramineae family.ResultsWe analyzed genome-wide transcriptional profiles of leaves of 5-week-old switchgrass plantlets grown via tissue culture after primary and secondary dehydration stresses (D1 and D2) and identified 16,551 novel lncRNAs, including 4554 annotated lncRNAs (targeting 3574 genes), and 11,997 unknown lncRNAs. Gene ontology and pathway enrichment analysis of annotated genes showed that the differentially expressed lncRNAs were related to abscisic acid (ABA) and ethylene (ETH) biosynthesis and signal transduction, and to starch and sucrose metabolism. The upregulated lncRNAs and genes were related to ABA synthesis and its signal transduction, and to trehalose synthesis. Meanwhile, lncRNAs and genes related to ETH biosynthesis and signal transduction were suppressed. LncRNAs and genes involved in ABA metabolism were verified using quantitative real-time PCR, and the endogenous ABA content was determined via high performance liquid chromatography mass spectrometry (HPLC-MS). These results showed that ABA accumulated significantly during dehydration stress, especially in D2. Furthermore, we identified 307 dehydration stress memory lncRNAs, and the ratios of different memory types in switchgrass were similar to those in Arabidopsis and maize.ConclusionsThe molecular responses of switchgrass lncRNAs to multiple dehydration stresses were researched systematically, revealing novel information about their transcriptional regulatory behavior. This study provides new insights into the response mechanism to dehydration stress in plants. The lncRNAs and pathways identified in this study provide valuable information for genetic modification of switchgrass and other crops.

Priming effect of root-applied silicon on the enhancement of induced resistance to the root-knot nematode Meloidogyne graminicola in rice

BackgroundSilicon (Si) can confer plant resistance to both abiotic and biotic stress. In the present study, the priming effect of Si on rice (Oryza sativa cv Nipponbare) against the root-knot nematode Meloidogyne graminicola and its histochemical and molecular impact on plant defense mechanisms were evaluated.ResultsSi amendment significantly reduced nematodes in rice roots and delayed their development, while no obvious negative effect on giant cells was observed. Increased resistance in rice was correlated with higher transcript levels of defense-related genes (OsERF1, OsEIN2 and OsACS1) in the ethylene (ET) pathway. Si amendment significantly reduced nematode numbers in rice plants with enhanced ET signaling but had no effect in plants deficient in ET signaling, indicating that the priming effects of Si were dependent on the ET pathway. A higher deposition of callose and accumulation of phenolic compounds were observed in rice roots after nematode attack in Si-amended plants than in the controls.ConclusionThese findings indicate that the priming effect may partially depend on the production of phenolic compounds and hydrogen peroxide. Further research is required to model the ethylene signal transduction pathway that occurs in the Si-plant-nematode interaction system and gain a better understanding of Si-induced defense in rice.

Transcription analysis of the ethylene receptor and CTR genes in tomato: The effects of on and off-vine ripening and 1-MCP

Ethylene, the main hormone regulating ripening in climacteric fruit, is perceived by the ethylene receptors starting a cascade of reactions of the ethylene signal transduction. In order to gain insight in the perception of ethylene during the ripening process, this work presents the transcriptional characterisation of the ethylene receptor (ETR) and CTR (CONSTITUTIVE TRIPPLE RESPONSE) genes of tomato fruit at different developmental stages and postharvest ripening conditions. Our results show that both ETR and CTR genes were differentially expressed when comparing on the vine ripening with off the vine (postharvest ripening) and in response to 1-MCP. Expression of the six ethylene receptors revealed SlETR3 and SlETR4 as the most expressed genes and together with SlETR6 to be the most ethylene-responsive, as they were the fastest to react to changes in conditions such as the 1-MCP application in detached fruit ripening off the vine. A climacteric pattern of expression similar to that of ethylene production itself was observed for most of the receptors and CTR genes during ripening, most strongly during postharvest ripening. All together our results suggest a dedicated regulation of the expression of ETRs and CTRs that allows the plant to precisely control the timing of ripening.

Transcript Profiling and Gene Identification Involved in the Ethylene Signal Transduction Pathways of Creeping Bentgrass (Agrostis stolonifera) during ISR Response Induced by Butanediol.

Creeping bentgrass (Agrostis stolonifera) is the preferred green lawn grass, with excellent turf characteristics but poor disease resistance. At present, the mechanisms of disease resistance in creeping bentgrass are poorly understood, especially the ethylene signal transduction pathway under the induced systemic resistance (ISR) response. In this study, butanediol (BDO), as a new type of disease-resistance compound, was applied to creeping bentgrass seedlings to induce the ISR response. Then, we measured ethylene production and related enzyme activities. Additionally, transcript profiling and gene identification were performed in association to ethylene signal transduction pathways. The changes of ethylene production and related enzyme 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) and 1-aminocyclopropane-1-carboxylic acid synthases (ACS) activities showed significant difference at 24 h after Rhizoctonia solani inoculation among five treatments of various BDO concentrations. After 100 µmol L−1 BDO treatment, ethylene production and related enzyme activities reached their peak levels. Additionally, 208,672 unigenes of creeping bentgrass were obtained by de novo assembly. In total, 15,903 annotated unigenes were grouped into 33 canonical pathways in the KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis. Among those, 1803 unigenes were classified as ‘signal transduction’. There were 6766 differentially expressed genes (DEGs) among B24 (inoculated-rhizobacteria in MS medium with 100 µmol L−1 BDO for 24 h), NB24, B72 and NB24 (no rhizobacteria in MS medium with 100 µmol L−1 BDO for 24 h) libraries, and 4,639 DEGs between B24 and B72 (inoculated-rhizobacteria in MS medium with 100 µmol L−1 BDO for 72 h) libraries, with 4489 DEGs in all three libraries. As suggested by the RT-PCR assay, the expression levels of ethylene-responsive and defense-related genes were variable among treated samples during the BDO-induced ISR responses. The expression levels of EIN, ERF, NPR1, PR3 and PR4 genes increased and reached their peaks in the first 24 h after R. solani infection in the BDO-induced ISR reaction compared with NB24 treatments. This results is consistent with the changes of important ethylene biosynthetic enzymes and ethylene concentrations during the BDO-induced ISR responses. We further found the intermediate substances for the signaling pathway, and the relationships between the expression levels of BDO-induced ISR disease-resistance genes and those of the response genes for ethylene signal pathway. Our findings present a genetic basis for systemic resistance of creeping bentgrass through transcriptomic analysis and our study provides a theoretical and practical basis for the improvement of turfgrass disease resistance and quality.

Transcript analyses of ethylene pathway genes during ripening of Chinese jujube fruit

The fruit of Chinese jujube (Ziziphus jujuba Mill.) is immensely popular worldwide, while its fleshy fruit has a very short shelf life and suffers serious postharvest damage. The fruit has been controversially classified as non-climacteric, though the mechanisms underlying its ripening behavior, particularly the role of ethylene, have remained unclear. In this study, low and stable ethylene production was detected during ripening of Z. jujuba ‘Dongzao’ fruit, with production increasing at the full maturity stage. To determine potential ripening behavior, the fruit of five cultivars were harvested at the white mature stage, and all exhibited a first decreasing and then moderately increasing respiration rate without concomitant climacteric-like ethylene production during shelf storage. Treatment with 1.0 μL L−1 1-methylcyclopropene (1-MCP) inhibited respiration and ethylene production in white mature fruit, though the effects of 100 μL L−1 exogenous ethylene were not significant. The transcript levels of genes involved in ethylene biosynthesis, perception, and signal transduction were not elevated during fruit-ripening onset but substantially increased at the full-red ripening stage. Moreover, expression of genes controlling ethylene biosynthesis and perception mainly occurred in an auto-inhibited System-1-like manner, but signaling pathway genes were minimally affected by exogenous ethylene or 1-MCP. These results show that the ripening of Chinese jujube is non-climacteric. The basal level of ethylene likely plays a minor role in ripening regulation but is necessary to maintain normal ripening. This study elucidates the effects of ethylene on jujube fruit ripening, characterizing the ripening of this fruit as non-climacteric, and also provides strategies for the improvement and maintenance of fruit quality and the extension of shelf life during postharvest storage.

Molecular and functional characterization of ShNAC1, an NAC transcription factor from Solanum habrochaites

NAC transcription factors (TFs) are important regulators of plant adaptation to abiotic stress. In this study, we functionally characterized an NAC TF, ShNAC1, from Solanum habrochaites. ShNAC1 was up-regulated by drought, cold, and salt stresses, and it displayed lower expression at the late stage of stress treatments than its orthologous gene in S. lycopersicum. Overexpression of ShNAC1 in tomato resulted in reduced cold, drought, and salt tolerance. Additionally, ShNAC1 displayed the highest expression in senescent leaf, and overexpressing ShNAC1 accelerated salt- and dark-induced leaf senescence. ShNAC1 was located in the nucleus without transactivation activity. RNA-seq analysis revealed that 81% (190 out of 234) differentially-expressed genes (DEGs) showed down-regulation in the transgenic line L2 compared with wild-type, suggesting that ShNAC1 may function as a transcriptional repressor. Among these down-regulated DEGs, many were involved in stress responses, such as SlHKT1;1, SlMAPKKK59, SlJA2, SlTIL, SlALDH2B1, etc. Noticeably, one ACS gene and three ACO genes involved in ethylene biosynthesis were up-regulated, while seven ERF genes in the ethylene signal transduction pathway were down-regulated in the transgenic lines, respectively. Our results suggested that ShNAC1 negatively regulates tolerance to abiotic stress in tomato probably by modulating the ethylene biosynthesis and signal transduction pathways.

Membrane protein MHZ3 stabilizes OsEIN2 in rice by interacting with its Nramp-like domain

The phytohormone ethylene regulates many aspects of plant growth and development. EIN2 is the central regulator of ethylene signaling, and its turnover is crucial for triggering ethylene responses. Here, we identified a stabilizer of OsEIN2 through analysis of the rice ethylene-response mutant mhz3. Loss-of-function mutations lead to ethylene insensitivity in etiolated rice seedlings. MHZ3 encodes a previously uncharacterized membrane protein localized to the endoplasmic reticulum. Ethylene induces MHZ3 gene and protein expression. Genetically, MHZ3 acts at the OsEIN2 level in the signaling pathway. MHZ3 physically interacts with OsEIN2, and both the N- and C-termini of MHZ3 specifically associate with the OsEIN2 Nramp-like domain. Loss of mhz3 function reduces OsEIN2 abundance and attenuates ethylene-induced OsEIN2 accumulation, whereas MHZ3 overexpression elevates the abundance of both wild-type and mutated OsEIN2 proteins, suggesting that MHZ3 is required for proper accumulation of OsEIN2 protein. The association of MHZ3 with the Nramp-like domain is crucial for OsEIN2 accumulation, demonstrating the significance of the OsEIN2 transmembrane domains in ethylene signaling. Moreover, MHZ3 negatively modulates OsEIN2 ubiquitination, protecting OsEIN2 from proteasome-mediated degradation. Together, these results suggest that ethylene-induced MHZ3 stabilizes OsEIN2 likely by binding to its Nramp-like domain and impeding protein ubiquitination to facilitate ethylene signal transduction. Our findings provide insight into the mechanisms of ethylene signaling.

Genomic Sequencing of Japanese Plum (Prunus salicina Lindl.) Mutants Provides a New Model for Rosaceae Fruit Ripening Studies.

It has recently been described that the Japanese plum “Santa Rosa” bud sport series contains variations in ripening pattern: climacteric, suppressed-climacteric and non-climacteric types. This provides an interesting model to study the role of ethylene and other key mechanisms governing fruit ripening, softening and senescence. The aim of the current study was to investigate such differences at the genomic level, using this series of plum bud sports, with special reference to genes involved in ethylene biosynthesis, signal transduction, and sugar metabolism. Genomic DNA, isolated from leaf samples of six Japanese plum cultivars (“Santa Rosa”, “July Santa Rosa”, “Late Santa Rosa”, “Sweet Miriam”, “Roysum”, and “Casselman”), was used to construct paired-end standard Illumina libraries. Sequences were aligned to the Prunus persica genome, and genomic variations (SNPs, INDELS, and CNV's) were investigated. Results determined 12 potential candidate genes with significant copy number variation (CNV), being associated with ethylene perception and signal transduction components. Additionally, the Maximum Likelihood (ML) phylogenetic tree showed two sorbitol dehydrogenase genes grouping into a distinct clade, indicating that this natural group is well-defined and presents high sequence identity among its members. In contrast, the ethylene group, which includes ACO1, ACS1, ACS4, ACS5, CTR1, ERF1, ERF3, and ethylene-receptor genes, was widely distributed and clustered into 10 different groups. Thus, ACS, ERF, and sorbitol dehydrogenase proteins potentially share a common ancestor for different plant genomes, while the expansion rate may be related to ancestral expansion rather than species-specific events. Based on the distribution of the clades, we suggest that gene function diversification for the ripening pathway occurred prior to family extension. We herein report all the frameshift mutations in genes involved in sugar transport and ethylene biosynthesis detected as well as the gene CNV implicated in ripening differences.

Transcriptome profiling reveals candidate genes associated with sex differentiation induced by night temperature in cucumber

Abstract The sex differentiation of cucumber directly affects cucumber fruit yield, and low night temperature (LT) promotes female flower differentiation. However, studies on the effects of LT on sex differentiation are scarce. To better understand this mechanism, we used transcriptomics to examine the expression patterns of genes related to female flower differentiation in the cucumber cultivar ‘C09-123’ under LT and high night temperature (HT). We identified a total of 1654 differentially expressed genes in response to LT. There were 1147 up-regulated genes and 507 down-regulated genes under LT compared with their expression under HT. Gene ontology (GO) analysis revealed that the differentially expressed genes were mainly involved in cellular process, metabolic process, response to stimulus process and other processes (biological process). Many of these differentially expressed genes (DEGs) were related to glucose metabolism, cysteine and methionine metabolism and the ethylene and auxin signal transduction pathway and were up-regulated under LT, which promotes female differentiation, compared with their expression level under HT. These results suggest that changes in these genes are likely to affect the corresponding metabolism, thus inducing the female flower differentiation of cucumber under LT. Ethylene and auxin play important roles in the induction of female flower differentiation under LT. This study provides valuable resources for further exploring the molecular basis of LT induction of female flower differentiation and for enabling targeted breeding strategies for developing varieties with superior strong female differentiation to achieve yield potential.

Comparative Analyses of the Transcriptome and Proteome of Comte de Paris and Smooth Cayenne to Improve the Understanding of Ethephon-Induced Floral Transition in Pineapple

Background/Aims: Ethylene is usually used to induce floral transition in pineapple. However, its successful induction in plants categorized as Cayenne is difficult or completely ineffective, and information concerned is limited. The present study was undertaken to investigate the molecular mechanisms underlying this obstacle. Methods: Transcriptome and proteome comparative analyses were performed to explore the important regulation and pathway variations after ethephon induction in the induction-easy ‘Comte de Paris’ (CP) and induction-hard ‘Smooth Cayenne’ (SC) cultivars via RNA-seq (RNA-sequencing) and iTRAQ (isobaric tags for relative and absolute quantification). Results: CP and SC exhibited basic differences at the transcriptomic and proteomic levels before ethephon treatment, including the expression of genes and proteins related to ethylene signal transduction. After ethephon induction, the expression of genes and proteins involved in plant ethylene signal transduction and carbohydrate metabolism responded more strongly in CP than in SC. The expression of the floral meristem identity (FMI) genes AG, TFL and FT exhibited greater changes in CP, and more transcription factors responded in SC. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that many differentially expressed genes (DEGs) in CP were annotated to terms and pathways involved in photoperiodism and shared components involved in carbohydrate metabolism and plant hormone signal transduction. Conclusion: These findings contribute to the understanding of the molecular mechanism underlying the variation between CP and SC in response to ethephon-mediated floral induction.

Comparative Transcriptome Analysis of Actinidia arguta Fruits Reveals the Involvement of Various Transcription Factors in Ripening

The fruit of Actinidia arguta is typically climacteric. During ripening, the fruits produce a large amount of ethylene. Although the molecular basis of climacteric fruit ripening has been extensively studied, some aspects such as its transcriptional regulation remain unclear. Here, we compared the transcriptomes of A. arguta fruits collected at commercial harvest (sample d0) and at 6 days after harvest (sample d6) using RNA-seq. A total of 3 659 differentially expressed genes (DEGs) between samples d0 and d6 were detected, of which 2 983 and 1 104 could be functionally annotated with Gene Ontology (GO) and Clusters of Orthologous Groups (COG) pathways. DEGs involved in ethylene biosynthesis and signal transduction were identified, including ACO (c79627), ERF061 (c105131), and ERF6 (c99193). Transcription factors such as ERF, bHLH, NAC, MADS, and MYB were also differentially expressed between samples d0 and d6. Selected DEGs were subjected to further analysis using quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and the results coincided with those of RNA-seq. Our data revealed additional transcription factors that are involved in the regulation of fruit ripening. These results provide useful information for future research on the transcriptional regulation of fruit ripening.

Ethylene production and constitutive expression of ethylene receptors and ethylene signal transduction during grain filling in apical and basal spikelets of compact-and lax-panicle rice (Oryza sativa) cultivars

Ethylene production and constitutive expression of ethylene receptors and ethylene signal transduction during grain filling in apical and basal spikelets of compact-and lax-panicle rice (Oryza sativa) cultivars

受容と信号伝達-エチレン : エチレンの受容と情報伝達機構( 最近の植物ホルモン研究の動向 I 受容と信号伝達)

受容と信号伝達-エチレン : エチレンの受容と情報伝達機構( 最近の植物ホルモン研究の動向 I 受容と信号伝達)

Silver nitrate modulates organogenesis in Brassica juncea (L.) through differential antioxidant defense and hormonal gene expression

Abstract Silver nitrate (AgNO3) is a known modulator of morphogenesis in plant cell and tissue culture but the underlying mechanism of its stimulatory effect on organogenesis is not clearly known. In Brassica juncea, we have studied AgNO3 induced high frequency shoot organogenesis and analyzed changes in antioxidant defense and, transcript profiling of hormone synthesis and signaling related genes. Hypocotyl explants cultured on medium with 2 mg/L BAP, 0.01 mg/L NAA and supplemented with 3 mg/L AgNO3 exhibited morphogenetic distinctness on 7 and 14th day and high frequency (95.89%) shoot organogenesis on 21st day of culture compared to medium without AgNO3 (14.6%). AgNO3 induced higher H2O2 content on 7th day (6.25 mM/g FW) compared to 14th (1.83 mM/g FW) and 21st day (0.65 mM/g FW) cultures whereas; both the SOD and CAT activities were induced and maintained during the entire culture period. Transcript profiling of ethylene and hormone synthesis-related genes suggested enhanced expression of ethylene signal transduction gene EIN2 in the absence of AgNO3 compared to that of AgNO3 treatment, indicating that AgNO3 could inhibit or nullify the ethylene response. The expression of cytokinin biosynthesis and negative regulator of auxin genes was also enhanced signifying that these may be involved in improved shoot regeneration. Taken together, it is suggested that AgNO3 application induces initial oxidative milieu followed by less-oxidized cellular environment and, upregulation of cytokinin receptor and negative regulator of auxin biosynthesis genes which may work in favour of improved shoot regeneration in Brassica juncea L.

Upregulation of Phosphatidylinositol 3-Kinase (PI3K) Enhances Ethylene Biosynthesis and Accelerates Flower Senescence in Transgenic Nicotiana tabacum L.

Phosphatidylinositol 3-kinase (PI3K) is a key enzyme that phosphorylates phosphatidylinositol at 3’-hydroxyl position of the inositol head group initiating the generation of several phosphorylated phosphatidylinositols, collectively referred to as phosphoinositides. The function of PI3K in plant senescence and ethylene signal transduction process was studied by expression of Solanum lycopersicum PI3K in transgenic Nicotiana tabacum, and delineating its effect on flower senescence. Detached flowers of transgenic tobacco plants with overexpressed Sl-PI3K (OX) displayed accelerated senescence and reduced longevity, when compared to the flowers of wild type plants. Flowers from PI3K-overexpressing plants showed enhanced ethylene production and upregulated expression of 1-aminocyclopropane-1-carboxylic acid oxidase 1 (ACO1). Real time polymerase chain reaction (PCR) analysis showed that PI3K was expressed at a higher level in OX flowers than in the control. Seedlings of OX-lines also demonstrated a triple response phenotype with characteristic exaggerated apical hook, shorter hypocotyls and increased sensitivity to 1-aminocyclopropane-1-carboxylate than the control wild type seedlings. In floral tissue from OX-lines, Solanum lycopersicum phosphatidylinositol 3-kinase green fluorescent protein (PI3K-GFP) chimera protein was localized primarily in stomata, potentially in cytoplasm and membrane adjacent to stomatal pores in the guard cells. Immunoblot analysis of PI3K expression in OX lines demonstrated increased protein level compared to the control. Results of the present study suggest that PI3K plays a crucial role in senescence by enhancing ethylene biosynthesis and signaling.

Genes involved in ethylene signal transduction in peach (Prunus persica) and their expression profiles during fruit maturation

Ethylene is an essential regulator of fruit development. However, the role of this phytohormone in the development and maturation of peach (Prunus persica L. Batsch) fruit has not been systematically examined. In this study, through BLAST analysis of tomato (Solanum lycopersicum) protein sequences against the peach genome database and transcriptome analysis of all APETALA2/Ethylene Responsive Factor (AP2/ERF) genes in peach, we identified 15 ethylene signal transduction genes and 15 AP2/ERF genes and examined their expression levels in SH (stony hard) peaches and MF (melting flesh) peaches during fruit maturation. We investigated the expression patterns of six genes, including one ETR-like gene (Prupe.1G034300) and five AP2/ERF genes (Prupe.1G037700, Prupe.2G289500, Prupe.3G240000, Prupe.5G061800, and Prupe.7G194400), through quantitative RT-PCR expression analysis. The transcript levels of these genes were lower at the early stages of fruit development and increased dramatically at stage S4 in MF peaches, while they remained low in SH peaches, which mirrors the pattern of changes observed in ethylene production. Treatment of MF (‘Zhongyoutao 13’, ‘CN13’) fruit at stage S4 II with 1-MCP was ineffective in blocking ethylene production, and the expression of these genes was inhibited by 1-MCP treatment in ‘CN13’ on day 1, further demonstrating that these genes are closely related to fruit ripening. We detected a slight change in fruit firmness in ‘CN13’ after 1-MCP treatment, whereas ethylene production was not affected. By contrast, the transcript profile of gene Prupe.5G090800 exhibited the opposite trend. The comprehensive data generated in this study will improve our understanding of the ethylene receptor genes and ERF genes in peach and lay the foundation for further exploring the mechanisms underlying peach fruit ripening and softening.

Physiological and Transcriptional Changes of Three Citrus Rootstock Seedlings under Iron Deficiency

Iron is an essential micronutrient for plants, and plants have evolved adaptive mechanisms to improve iron acquisition from soils. Grafting on iron deficiency-tolerant rootstock is an effective strategy to prevent iron deficiency-chlorosis in fruit-tree crops. To determine the mechanisms underlying iron uptake in iron deficiency, two iron deficiency-tolerant citrus rootstocks, Zhique (ZQ) and Xiangcheng (XC), as well as iron deficiency-sensitive rootstock trifoliate orange (TO) seedlings were studied. Plants were grown in hydroponics system for 100 days, having 50 μM iron (control) and 0 μM iron (iron deficiency) nutrient solution. Under iron deficiency, more obvious visual symptoms of iron chlorosis were observed in the leaves of TO, whereas slight symptoms were observed in ZQ and XC. This was further supported by the lower chlorophyll concentration in the leaves of TO than in leaves of ZQ and XC. Ferrous iron showed no differences among the three citrus rootstock roots, whereas ferrous iron was significantly higher in leaves of ZQ and XC than TO. The specific iron absorption rate and leaf iron proportion were significantly higher in ZQ and XC than in TO, suggesting the iron deficiency tolerance can be explained by increased iron uptake in roots of ZQ and XC, allowed by subsequent translocation to shoots. In transcriptome analysis, 29, 298, and 500 differentially expressed genes (DEGs) in response to iron deficiency were identified in ZQ, XC, and TO, respectively (Fold change ≥ 2 and Probability ≥ 0.8 were used as thresholds to identify DEGs). A Gene Ontology analysis suggested that several genotype-specific biological processes are involved in response to iron deficiency. Genes associated with cell wall biosynthesis, ethylene and abscisic acid signal transduction pathways were involved in iron deficiency responses in citrus rootstocks. The results of this study provide a basis for future analyses of the physiological and molecular mechanisms of the tolerance of different citrus rootstocks to iron deficiency.

Genome-wide analysis of banana MADS-box family closely related to fruit development and ripening

Proteins encoded by MADS-box genes are important transcription factors involved in the regulation of flowering plant growth and development. Currently, no systematic information exists regarding the MADS-box family in the important tropical fruit banana. Ninety-six MADS-box genes were identified from the banana (Pahang) A genome. Phylogenetic analysis indicated that Musa acuminata MCM1-AGAMOUS- DEFICIENS-SRF (MaMADS) could be divided into MIKCc, MIKC*, Mα/β and Mγ groups. MIKCc could be further divided into 11 subfamilies, which was further supported by conserved motif and gene structure analyses. Transcriptome analysis on the Feng Jiao (FJ) and BaXi Jiao (BX) banana cultivars revealed that MaMADS genes are differentially expressed in various organs, at different fruit development and ripening stages, indicating the involvement of these genes in fruit development and ripening processes. Interactive network analysis indicated that MaMADS24 and 49 not only interacted with MaMADS proteins themselves, but also interacted with hormone-response proteins, ethylene signal transduction and biosynthesis-related proteins, starch biosynthesis proteins and metabolism-related proteins. This systematic analysis identified candidate MaMADS genes related to fruit development and ripening for further functional characterization in plants, and also provided new insights into the transcriptional regulation of MaMADS genes, facilitating the future genetic manipulation of MADS-mediated fruit development and ripening.

Mechanisms regulating ethylene signal transduction in plants

Plant hormone ethylene regulates a wide range of physiological processes during plant development and coordinates plant responses to stresses. Ethylene controls important characteristics of agricultural crops such as the fruit ripening rate and plant resistance to adverse conditions. Understanding the molecular mechanisms of ethylene’s action is one of the actual questions in both the fundamental and applied contexts. Ethylene biosynthesis from methionine and the main steps of the transduction of the ethylene signal from membrane receptors to effector genes have been studied in detail and widely discussed in many reviews. At the same time, the genetic regulation of these two processes has been poorly studied, although it is responsible for the rapid and accurate reaction of plants to various endogenous and external stimuli and for the diversity of the physiological responses of plants to ethylene. This review summarizes the information about the regulatory mechanisms of ethylene biosynthesis and signal transduction. The key factors of transcriptional and post-translational regulation, which control the expression and stability of the main components of the biosynthesis and signaling pathways of ethylene, and the multiple feedbacks supplementing the linear model of ethylene’s signaling pathway are described. Special attention is paid to the role of the ethylene crosstalk with other plant hormones. Different mechanisms of hormonal interaction are illustrated by examples of the synergy or antagonism between ethylene and auxin, jasmonates, cytokinins, and brassinosteroids. The possible molecular bases of the diversity of the physiological responses to ethylene are also discussed.