Cross-Talk Signaling in Rice During Combined Drought and Bacterial Blight Stress

Drought: A context-dependent damper and aggravator of plant diseases

Drought dynamically influences the interactions between plants and pathogens, thereby affecting disease outbreaks. Understanding the intricate mechanistic aspects of the multiscale interactions among plants, pathogens, and the environment-known as the disease triangle-is paramount for enhancing the climate resilience of crop plants. In this review, we systematically compile and comprehensively analyse current knowledge on the influence of drought on the severity of plant diseases. We emphasise that studying these stresses in isolation is not sufficient to predict how plants respond to combined stress from both drought and pathogens. The impact of drought and pathogens on plants is complex and multifaceted, encompassing the activation of antagonistic signalling cascades in response to stress factors. The nature, intensity, and temporality of drought and pathogen stress occurrence significantly influence the outcome of diseases. We delineate the drought-sensitive nodes of plant immunity and highlight the emerging points of crosstalk between drought and defence signalling under combined stress. The limited mechanistic understanding of these interactions is acknowledged as a key research gap in this area. The information synthesised herein will be crucial for crafting strategies for the accurate prediction and mitigation of future crop disease risks, particularly in the context of a changing climate.

Screening for brown-spot disease and drought stress response and identification of dual-stress responsive genes in rice cultivars of Northeast India

Rice cultivation in Northeast India (NEI) primarily relies on rainfed conditions, making it susceptible to severe drought spells that promote the onset of brown spot disease (BSD) caused by Bipolaris oryzae. This study investigates the response of prevalent rice cultivars of NEI to the combined stress of drought and B. oryzae infection. Morphological, physiological, biochemical, and molecular changes were recorded post-stress imposition. Qualitative assessment of reactive oxygen species through DAB (3,3-diaminobenzidine) assay confirmed the elicitation of plant defense responses. Based on drought scoring system and biochemical analyses, the cultivars were categorized into susceptible (Shasharang and Bahadur), moderately susceptible (Gitesh and Ranjit), and moderately tolerant (Kapilee and Mahsuri) groups. Antioxidant enzyme accumulation (catalase, guaiacol peroxidase) and osmolyte (proline) levels increased in all stressed plants, with drought-tolerant cultivars exhibiting higher enzyme activities, indicating stress mitigation efforts. Nevertheless, electrolyte leakage and lipid peroxidation rates increased in all stressed conditions, though variations were observed among stress types. Based on findings from a previous transcriptomic study, a total of nine genes were chosen for quantitative real-time PCR analysis. Among these, OsEBP89 appeared as a potential negative regulatory gene, demonstrating substantial upregulation in the susceptible cultivars at both 48 and 72 h post-treatment (hpt). This finding suggests that OsEBP89 may play a role in conferring drought-induced susceptibility to BSD in the rice cultivars being investigated.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01447-4.

Above-and below-ground feedback loop of maize is jointly enhanced by plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi in drier soil

Drought is a potent abiotic stressor that arrests crop growth, significantly affecting crop health and yields. The arbuscular mycorrhizal fungi (AMF), and plant growth-promoting rhizobacteria (PGPR) can offer to protect plants from stressful environments through improving water, and nutrient use efficiency by strengthening plant root structure and harnessing favorable rhizosphere environments. When Acaulospora laevis (AMF) and Bacillus subtilus (PGPR) are introduced in combination, enhanced root growth and beneficial microbial colonization can mitigate drought stress. To assess this potential, a pot experiment was done with maize (Zea mays L.) to explore the effects of A. laevis and B. subtilus under different water levels (well-watered = 80 %; moderate water stress = 55 %; and severe water stress = 35 %) on maize yield, soil microbial activities, nutrients contents, root, and leaf functioning. Plants exposed to severe drought stress hampered their root and leaf functioning, and reduced grain yield compared with control plants. Combined use of AMF and PGPR increased root colonization (104.6 %-113.2 %) and microbial biomass carbon (36.38 %-40.23 %) under moderate to severe drought conditions over control. Higher root colonization was strongly linked with elevated ACC (aminocyclopropane-1-carboxylic acid) production, subsequently enhancing water use efficiency (21.62 %-12.77 %), root hydraulic conductivity (1.9 %-1.4 %) and root nutrient uptake under moderate to severe drought conditions. Enhanced nutrient uptake further promoted leaf photosynthetic rate by 27.3 %-29.8 % under moderate and severe drought stress. Improving leaf and root physiological functioning enhanced maize grain yield under stressful environments. Furthermore, co-inoculation with AMF-PGPR reduced cellular damage by lowering oxidative enzyme levels and increasing antioxidative enzyme activities, improving plant performance and grain yield under stressful environments. Conclusively, the synergistic interaction of AMF with PGPR ensured plant stress tolerance by reducing cellular injury, facilitating root-leaf functioning, enhancing nutrient-water-use-efficiencies, and increasing yield under drought stress.

Polysome-bound mRNAs and translational mechanisms regulate drought tolerance in rice

Plants evolved several acquired tolerance traits for drought stress adaptation to maintain the cellular homeostasis. Drought stress at the anthesis stage in rice affects productivity due to the inefficiency of protein synthesis machinery. The effect of translational mechanisms on different pathways involved in cellular tolerance plays an important role. We report differential responses of translation-associated mechanisms in rice using polysome bound mRNA sequencing at anthesis stage drought stress in resistant Apo and sensitive IR64 genotypes. Apo maintained higher polysomes with 60 S-to-40 S and polysome-to-monosome ratios which directly correlate with protein levels under stress. IR64 has less protein levels under stress due to defective translation machinery and reduced water potential. Many polysome-bound long non-coding RNAs (lncRNA) were identified in both genotypes under drought, influencing translation. Apo had higher levels of N6-Methyladenosine (m6A) mRNA modifications that contributed for sustained translation. Translation machinery in Apo could maintain higher levels of photosynthetic machinery-associated proteins in drought stress, which maintain gas exchange, photosynthesis and yield under stress. The protein stability and ribosome biogenesis mechanisms favoured improved translation in Apo. The phytohormone signalling and transcriptional responses were severely affected in IR64. Our results demonstrate that, the higher translation ability of Apo favours maintenance of photosynthesis and physiological responses that are required for drought stress adaptation.

Strategies of Molecular Signal Integration for Optimized Plant Acclimation to Stress Combinations

Plant growth and survival in their natural environment require versatile mitigation of diverse threats. The task is especially challenging due to the largely unpredictable interaction of countless abiotic and biotic factors. To resist an unfavorable environment, plants have evolved diverse sensing, signaling, and adaptive molecular mechanisms. Recent stress studies have identified molecular elements like secondary messengers (ROS, Ca2+, etc.), hormones (ABA, JA, etc.), and signaling proteins (SnRK, MAPK, etc.). However, major gaps remain in understanding the interaction between these pathways, and in particular under conditions of stress combinations. Here, we highlight the challenge of defining "stress" in such complex natural scenarios. Therefore, defining stress hallmarks for different combinations is crucial. We discuss three examples of robust and dynamic plant acclimation systems, outlining specific plant responses to complex stress overlaps. (a) The high plasticity of root system architecture is a decisive feature in sustainable crop development in times of global climate change. (b) Similarly, broad sensory abilities and apparent control of cellular metabolism under adverse conditions through retrograde signaling make chloroplasts an ideal hub. Functional specificity of the chloroplast-associated molecular patterns (ChAMPs) under combined stresses needs further focus. (c) The molecular integration of several hormonal signaling pathways, which bring together all cellular information to initiate the adaptive changes, needs resolving.

Exogenous application of nanocarrier-mediated double-stranded RNA manipulates physiological traits and defence response against bacterial diseases

Stability and delivery are major challenges associated with exogenous double-stranded RNA (dsRNA) application into plants. We report the encapsulation and delivery of dsRNA in cationic poly-aspartic acid-derived polymer (CPP6) into plant cells. CPP6 stabilizes the dsRNAs during long exposure at varied temperatures and pH, and protects against RNase A degradation. CPP6 helps dsRNA uptake through roots or foliar spray and facilitates systemic movement to induce endogenous gene silencing. The fluorescence of Arabidopsis GFP-overexpressing transgenic plants was significantly reduced after infiltration with gfp-dsRNA-CPP6 by silencing of the transgene compared to plants treated only with gfp-dsRNA. The plant endogenous genes flowering locus T (FT) and phytochrome interacting factor 4 (PIF4) were downregulated by a foliar spray of ft-dsRNA-CPP6 and pif4-dsRNA-CPP6 in Arabidopsis, with delayed flowering and enhanced biomass. The rice PDS gene targeted by pds-dsRNA-CPP6 through root uptake was effectively silenced and plants showed a dwarf and albino phenotype. The NaCl-induced OsbZIP23 was targeted through root uptake of bzip23-dsRNA-CPP6 and showed reduced transcripts and seedling growth compared to treatment with naked dsRNA. The negative regulators of plant defence SDIR1 and SWEET14 were targeted through foliar spray to provide durable resistance against bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo). Overall, the study demonstrates that transient silencing of plant endogenous genes using polymer-encapsulated dsRNA provides prolonged and durable resistance against Xoo, which could be a promising tool for crop protection and for sustaining productivity.

Stress combinations and their interactions in plants database: a one-stop resource on combined stress responses in plants

We have developed a compendium and interactive platform, named Stress Combinations and their Interactions in Plants Database (SCIPDb; http://www.nipgr.ac.in/scipdb.php), which offers information on morpho-physio-biochemical (phenome) and molecular (transcriptome and metabolome) responses of plants to different stress combinations. SCIPDb is a plant stress informatics hub for data mining on phenome, transcriptome, trait-gene ontology, and data-driven research for advancing mechanistic understanding of combined stress biology. We analyzed global phenome data from 939 studies to delineate the effects of various stress combinations on yield in major crops and found that yield was substantially affected under abiotic-abiotic stresses. Transcriptome datasets from 36 studies hosted in SCIPDb identified novel genes, whose roles have not been earlier established in combined stress. Integretome analysis under combined drought-heat stress pinpointed carbohydrate, amino acid, and energy metabolism pathways as the crucial metabolic, proteomic, and transcriptional components in plant tolerance to combined stress. These examples illustrate the application of SCIPDb in identifying novel genes and pathways involved in combined stress tolerance. Further, we showed the application of this database in identifying novel candidate genes and pathways for combined drought and pathogen stress tolerance. To our knowledge, SCIPDb is the only publicly available platform offering combined stress-specific omics big data visualization tools, such as an interactive scrollbar, stress matrix, radial tree, global distribution map, meta-phenome analysis, search, BLAST, transcript expression pattern table, Manhattan plot, and co-expression network. These tools facilitate a better understanding of the mechanisms underlying plant responses to combined stresses.

Differential Participation of Plant Ribosomal Proteins from the Small Ribosomal Subunit in Protein Translation under Stress

Upon exposure to biotic and abiotic stress, plants have developed strategies to adapt to the challenges imposed by these unfavorable conditions. The energetically demanding translation process is one of the main elements regulated to reduce energy consumption and to selectively synthesize proteins involved in the establishment of an adequate response. Emerging data have shown that ribosomes remodel to adapt to stresses. In Arabidopsis thaliana, ribosomes consist of approximately eighty-one distinct ribosomal proteins (RPs), each of which is encoded by two to seven genes. Recent research has revealed that a mutation in a given single RP in plants can not only affect the functions of the RP itself but can also influence the properties of the ribosome, which could bring about changes in the translation to varying degrees. However, a pending question is whether some RPs enable ribosomes to preferentially translate specific mRNAs. To reveal the role of ribosomal proteins from the small subunit (RPS) in a specific translation, we developed a novel approach to visualize the effect of RPS silencing on the translation of a reporter mRNA (GFP) combined to the 5'UTR of different housekeeping and defense genes. The silencing of genes encoding for NbRPSaA, NbRPS5A, and NbRPS24A in Nicotiana benthamiana decreased the translation of defense genes. The NbRACK1A-silenced plant showed compromised translations of specific antioxidant enzymes. However, the translations of all tested genes were affected in NbRPS27D-silenced plants. These findings suggest that some RPS may be potentially involved in the control of protein translation.

Walking through crossroads-rice responses to heat and biotic stress interactions

Rice, the most important source of calories for humans is prone to severe yield loss due to changing climate including heat stress. Additionally, rice encounters biotic stresses in conjunction with heat stress, which exacerbates the adverse effects, and exponentially increase such losses. Several investigations have identified biotic and heat stress-related quantitative trait loci (QTLs) that may contribute to improved tolerance to these stresses. However, a significant knowledge gap exists in identifying the genomic regions imparting tolerance against combined biotic and heat stress. Hereby, we are presenting a conceptual meta-analysis identifying genomic regions that may be promising candidates for enhancing combined biotic and heat stress tolerance in rice. Fourteen common genomic regions were identified along chromosomes 1, 2, 3, 4, 6, 10 and 12, which harbored 1265 genes related to heat stress and defense responses in rice. Further, the meta expression analysis revealed 24 differentially expressed genes (DEGs) involved in calcium-mediated stress signaling including transcription factors Myb, bHLH, ROS signaling, molecular chaperones HSP110 and pathogenesis related proteins. Additionally, we also proposed a hypothetical model based on GO and MapMan analysis representing the pathways intersecting heat and biotic stresses. These DEGs can be potential candidate genes for improving tolerance to combined biotic and heat stress in rice. We present a framework highlighting plausible connecting links (QTLs/genes) between rice response to heat stress and different biotic factors associated with yield, that can be extended to other crops.

Effect of prior drought and heat stress on Camellia sinensis transcriptome changes to Ectropis oblique (Lepidoptera: Geometridae) resistance

Tea plants are continuously confronted with a wide range of biotic and abiotic stressors in the field, which can occur concurrently or sequentially. To elucidate the molecular mechanisms in responses to such individual and combined stresses, we used RNAseq to compare the temporal changes in the transcriptome of Camellia sinensis to Ectropis oblique Prout alone or in combination with exposure to drought and heat. Compared with the individual stress, tea plants exhibit significant differences in transcriptome profiles under the combined stresses. Additionally, many unique genes exhibited significant differences in expression in individual and combined stress conditions. Our research showed novel insights into the molecular mechanisms of E. oblique Prout resistance in tea plants and provided a valuable resource for developing tea varieties with broad spectrum stress tolerance.

Transcriptomic responses under combined bacterial blight and drought stress in rice reveal potential genes to improve multi-stress tolerance

BACKGROUND

The unprecedented drought and frequent occurrence of pathogen infection in rice is becoming more due to climate change. Simultaneous occurrence of stresses lead to more crop loss. To cope up multiple stresses, the durable resistant cultivars needs to be developed, by identifying relevant genes from combined biotic and abiotic stress exposed plants.

RESULTS

We studied the effect of drought stress, bacterial leaf blight disease causing Xanthomonas oryzae pv. oryzae (Xoo) pathogen infection and combined stress in contrasting BPT5204 and TN1 rice genotypes. Mild drought stress increased Xoo infection irrespective of the genotype. To identify relevant genes that could be used to develop multi-stress tolerant rice, RNA sequencing from individual drought, pathogen and combined stresses in contrasting genotypes has been developed. Many important genes are identified from resistant genotype and diverse group of genes are differentially expressed in contrasting genotypes under combined stress. Further, a meta-analysis from individual drought and Xoo pathogen stress from public domain data sets narrowed- down candidate differentially expressed genes. Many translation associated genes are differentially expressed suggesting their extra-ribosomal function in multi-stress adaptation. Overexpression of many of these genes showed their relevance in improving stress tolerance in rice by different scientific groups. In combined stress, many downregulated genes also showed their relevance in stress adaptation when they were over-expressed.

CONCLUSIONS

Our study identifies many important genes, which can be used as molecular markers and targets for genetic manipulation to develop durable resistant rice cultivars. Strategies should be developed to activate downregulated genes, to improve multi-stress tolerance in plants.

Genomic regions and candidate genes selected during the breeding of rice in Vietnam

Vietnam harnesses a rich diversity of rice landraces adapted to a range of conditions, which constitute a largely untapped source of diversity for the continuous improvement of cultivars. We previously identified a strong population structure in Vietnamese rice, which is captured in five Indica and four Japonica subpopulations, including an outlying Indica‐5 group. Here, we leveraged that strong differentiation and 672 native rice genomes to identify genomic regions and genes putatively selected during the breeding of rice in Vietnam. We identified significant distorted patterns in allele frequency (XP‐CLR) and population differentiation scores (F_ST) resulting from differential selective pressures between native subpopulations, and later annotated them with QTLs previously identified by GWAS in the same panel. We particularly focussed on the outlying Indica‐5 subpopulation because of its likely novelty and differential evolution, where we annotated 52 selected regions, which represented 8.1% of the rice genome. We annotated the 4576 genes in these regions and selected 65 candidate genes as promising breeding targets, several of which harboured alleles with nonsynonymous substitutions. Our results highlight genomic differences between traditional Vietnamese landraces, which are likely the product of adaption to multiple environmental conditions and regional culinary preferences in a very diverse country. We also verified the applicability of this genome scanning approach to identify potential regions harbouring novel loci and alleles to breed a new generation of sustainable and resilient rice.

Identification of major candidate genes for multiple abiotic stress tolerance at seedling stage by network analysis and their validation by expression profiling in rice (Oryza sativa L.)

A wealth of microarray and RNA-seq data for studying abiotic stress tolerance in rice exists but only limited studies have been carried out on multiple stress-tolerance responses and mechanisms. In this study, we identified 6657 abiotic stress-responsive genes pertaining to drought, salinity and heat stresses from the seedling stage microarray data of 83 samples and used them to perform unweighted network analysis and to identify key hub genes or master regulators for multiple abiotic stress tolerance. Of the total 55 modules identified from the analysis, the top 10 modules with 8-61 nodes comprised 239 genes. From these 10 modules, 10 genes common to all the three stresses were selected. Further, based on the centrality properties and highly dense interactions, we identified 7 intra-modular hub genes leading to a total of 17 potential candidate genes. Out of these 17 genes, 15 were validated by expression analysis using a panel of 4 test genotypes and a pair of standard check genotypes for each abiotic stress response. Interestingly, all the 15 genes showed upregulation under all stresses and in all the genotypes, suggesting that they could be representing some of the core abiotic stress-responsive genes. More pertinently, eight of the genes were found to be co-localized with the stress-tolerance QTL regions. Thus, in conclusion, our study not only provided an effective approach for studying abiotic stress tolerance in rice, but also identified major candidate genes which could be further validated by functional genomics for abiotic stress tolerance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03182-7.

Comparative Transcriptome Analysis of Rice Resistant and Susceptible Genotypes to Xanthomonas oryzae pv. oryzae Identifies Novel Genes to Control Bacterial Leaf Blight

The bacterial leaf blight in rice caused by Xanthomonas oryzae pv. oryzae (Xoo) affects crop losses worldwide. In spite of developing resistant varieties by introgressing different Xa genes, the occurrence of diseases is evident. Here we report identification of several genes that are associated with improved plant immunity against Xoo in a resistant genotype BPT-5204 in comparison with susceptible genotype TN-1. The RNA sequencing information was developed to identify the genes that could provide durable resistance in rice. Xoo-resistant rice genotype BPT-5204 with Xa 5, 13 and 21 genes is compared with sensitive Taichung Native 1 (TN-1) to identify the genetic pathways and gene networks involved in resistance mechanisms. The higher levels of salicylic acid resulted in upregulation of many pathogenesis-related (PR) and redox protein encoding transcripts which resulted in higher hypersensitive response in BPT-5204. Many Serine/threonine protein kinase, leucine-rich repeat (LRR) transmembrane protein kinase, protein kinase family genes, Wall-associated kinase (WAK) were upregulated that resulted in activation of bZIP, WRKY, MYB, DOF and HSFs transcription factors that are associated with improved plant immunity. The study provided roles of many genes and their associated plant immunity pathways that can be used for developing resistant rice cultivars.

Responses to Drought Stress Modulate the Susceptibility to Plasmopara viticola in Vitis vinifera Self-Rooted Cuttings

Climate change will increase the occurrence of plants being simultaneously subjected to drought and pathogen stress. Drought can alter the way in which plants respond to pathogens. This research addresses how grapevine responds to the concurrent challenge of drought stress and Plasmopara viticola, the causal agent of downy mildew, and how one stress affects the other. Self-rooted cuttings of the drought-tolerant grapevine cultivar Xynisteri and the drought-sensitive cultivar Chardonnay were exposed to full or deficit irrigation (40% of full irrigation) and artificially inoculated with P. viticola in vitro or in planta. Leaves were sampled at an early infection stage to determine the influence of the single and combined stresses on oxidative parameters, chlorophyll, and phytohormones. Under full irrigation, Xynisteri was more susceptible to P. viticola than the drought-sensitive cultivar Chardonnay. Drought stress increased the susceptibility of grapevine leaves inoculated in vitro, but both cultivars showed resistance against P. viticola when inoculated in planta. Abscisic acid, rather than jasmonic acid and salicylic acid, seemed to play a prominent role in this resistance. The irrigation-dependent susceptibility observed in this study indicates that the practices used to mitigate the effects of climate change may have a profound impact on plant pathogens.

Maize Responses Challenged by Drought, Elevated Daytime Temperature and Arthropod Herbivory Stresses: A Physiological, Biochemical and Molecular View

Maize (Zea mays L.) is one of the main cereals grown around the world. It is used for human and animal nutrition and also as biofuel. However, as a direct consequence of global climate change, increased abiotic and biotic stress events have been reported in different regions of the world, which have become a threat to world maize yields. Drought and heat are environmental stresses that influence the growth, development, and yield processes of maize crops. Plants have developed dynamic responses at the physiological, biochemical, and molecular levels that allow them to escape, avoid and/or tolerate unfavorable environmental conditions. Arthropod herbivory can generate resistance or tolerance responses in plants that are associated with inducible and constitutive defenses. Increases in the frequency and severity of abiotic stress events (drought and heat), as a consequence of climate change, can generate critical variations in plant-insect interactions. However, the behavior of herbivorous arthropods under drought scenarios is not well understood, and this kind of stress may have some positive and negative effects on arthropod populations. The simultaneous appearance of different environmental stresses and biotic factors results in very complex plant responses. In this review, recent information is provided on the physiological, biochemical, and molecular responses of plants to the combination of drought, heat stress, and the effect on some arthropod pests of interest in the maize crop.

Ribosomal protein QM/RPL10 positively regulates defence and protein translation mechanisms during nonhost disease resistance

Ribosomes play an integral part in plant growth, development, and defence responses. We report here the role of ribosomal protein large (RPL) subunit QM/RPL10 in nonhost disease resistance. The RPL10-silenced Nicotiana benthamiana plants showed compromised disease resistance against nonhost pathogen Pseudomonas syringae pv. tomato T1. The RNA-sequencing analysis revealed that many genes involved in defence and protein translation mechanisms were differentially affected due to silencing of NbRPL10. Arabidopsis AtRPL10 RNAi and rpl10 mutant lines showed compromised nonhost disease resistance to P. syringae pv. tomato T1 and P. syringae pv. tabaci. Overexpression of AtRPL10A in Arabidopsis resulted in reduced susceptibility against host pathogen P. syringae pv. tomato DC3000. RPL10 interacts with the RNA recognition motif protein and ribosomal proteins RPL30, RPL23, and RPS30 in the yeast two-hybrid assay. Silencing or mutants of genes encoding these RPL10-interacting proteins in N. benthamiana or Arabidopsis, respectively, also showed compromised disease resistance to nonhost pathogens. These results suggest that QM/RPL10 positively regulates the defence and translation-associated genes during nonhost pathogen infection.

OsEUL Lectin Gene Expression in Rice: Stress Regulation, Subcellular Localization and Tissue Specificity

The Euonymus lectin (EUL) family is a unique group of carbohydrate-binding proteins that is omnipresent in plants. Sequences encoding EUL-related lectins have been retrieved from all completely sequenced plant genomes. The rice (Oryza sativa) genome contains 5 functional EUL genes referred to as OsEULS2, OsEULS3, OsEULD1a, OsEULD1b, and OsEULD2. In this study we focused on the tissue specific expression, stress inducibility and subcellular localization of the rice EULs. Even though the EUL domain sequence is highly conserved among the rice EULs (at least 80% sequence similarity) different biotic and abiotic stress treatments yielded unique responses for the different EULs. Transcript levels for OsEULs were differentially affected by drought and salt stress, ABA treatment, pathogen infection or insect infestation. Analysis of promoter activity revealed differential expression and tissue specificity for the 5 OsEUL genes, with most expression observed in the vascular system of roots and shoots, as well as in the root tips and seeds. At cell level, all OsEULs are located in the nucleus whereas OsEULD1b and OsEULD2 also locate to the cytoplasm. This paper contributes to the functional characterization of the EULs and provides insight in the biological importance of this family of proteins for rice.