Germination Of Rice Research Articles

Allelopathic Potential of Cassava (Manihot esculenta L.) Extracts on Germination and Seedling Growth of Selected Weeds and Aerobic Rice

Weed infestation is a major problem in the aerobic rice system due to the lack of standing water that could prevent the growth of weeds. To reduce heavy reliance on herbicide, this research aims to determine the potential of cassava allelopathy for inhibition of weeds in aerobic rice. The allelopathic potential of cassava extracts on the germination and growth of tested weed species (Eleusine indica, Ageratum conyzoides, and Cyperus distans) and aerobic rice (Oryza sativa) was conducted in the laboratory. The results showed that increasing the aqueous extract concentrations of cassava extracts inhibited the germination and seedling growth of tested weeds, suggesting the allelopathic effects of cassava extracts are concentration dependent. The degree of phytotoxicity of different vegetative parts of cassava can be classified in order of decreasing inhibition as follows: leaf, stem, tuber, and tuber peel. Aqueous leaf extract of cassava at a concentration of 0.5% (w/v) provided complete inhibition on A. conyzoides, E. indica, and C. distansgermination whereas 25% to 100% inhibition on the shoot growth was recorded. By contrast, the shoot growth and germination of aerobic rice were not affected. These results suggest that the cassava leaf extracts contain water-soluble allelochemicals for inhibition on A. conyzoides, E. indica, and C. distans in aerobic rice.

Exogenous Melatonin Activates Antioxidant Systems to Increase the Ability of Rice Seeds to Germinate under High Temperature Conditions.

High temperatures are a major concern that limit rice germination and plant growth. Although previous studies found that melatonin can promote seed germination, the physiological regulation mechanism by which exogenous melatonin mediates high temperature tolerance during rice seed germination is still largely unknown. In order to overcome these challenges, the present study investigates the effects of melatonin on the characteristics of rice seed germination as well as on antioxidant properties, under different high temperature conditions. The results show that 100 μM melatonin seed-soaking treatment under high temperature conditions effectively improves the germination potential, the germination index, and the vigor index of rice seeds; increases the length of the shoot and the root; improves the activity of the antioxidant enzymes; and significantly reduces the malondialdehyde content. The gray relational grade of the shoot peroxidase activity and the melatonin soaking treatment was the highest, which was used to evaluate the effect of melatonin on the heat tolerance of rice. The subordinate function method was used to comprehensively evaluate the tolerance, and the results show that the critical concentration of melatonin is 100 μM, and the critical interactive treatment is the germination at 38 °C and followed by the recovery at 26 °C for 1 day + 100 μM. In conclusion, 100 μM of melatonin concentration improved the heat resistance of rice seeds by enhancing the activity of the antioxidant enzymes.

Exogenous SA Affects Rice Seed Germination under Salt Stress by Regulating Na+/K+ Balance and Endogenous GAs and ABA Homeostasis

Salinity reduces agricultural productivity majorly by inhibiting seed germination. Exogenous salicylic acid (SA) can prevent the harm caused to rice by salinity, but the mechanisms by which it promotes rice seed germination under salt stress are unclear. In this study, the inhibition of germination in salt-sensitive Nipponbare under salt stress was greater than that in salt-tolerant Huaidao 5. Treatment with exogenous SA significantly improved germination of Nipponbare, but had little effect on Huaidao 5. The effects of exogenous SA on ion balance, metabolism of reactive oxygen species (ROS), hormone homeostasis, starch hydrolysis, and other physiological processes involved in seed germination of rice under salt stress were investigated. Under salt stress, Na+ content and the Na+/K+ ratio in rice seeds increased sharply. Seeds were subjected to ion pressure, which led to massive accumulation of H2O2, O2−, and malonaldehyde (MDA); imbalanced endogenous hormone homeostasis; decreased gibberellic acid (GA1 and GA4) content; increased abscisic acid (ABA) content; inhibition of α-amylase (EC 3.2.1.1) activity; and slowed starch hydrolysis rate, all which eventually led to the inhibition of the germination of rice seeds. Exogenous SA could effectively enhance the expression of OsHKT1;1, OsHKT1;5, OsHKT2;1 and OsSOS1 to reduce the absorption of Na+ by seeds; reduce the Na+/K+ ratio; improve the activities of SOD, POD, and CAT; reduce the accumulation of H2O2, O2−, and MDA; enhance the expression of the GA biosynthetic genes OsGA20ox1 and OsGA3ox2; inhibit the expression of the ABA biosynthetic gene OsNCED5; increase GA1 and GA4 content; reduce ABA content; improve α-amylase activity, and increase the content of soluble sugars. In summary, exogenous SA can alleviate ion toxicity by reducing Na+ content, thereby helping to maintain ROS and hormone homeostasis, promote starch hydrolysis, and provide sufficient energy for seed germination, all of which ultimately improves rice seed germination under salt stress. This study presents a feasible means for improving the germination of direct-seeded rice in saline soil.

NLP2-NR Module Associated NO Is Involved in Regulating Seed Germination in Rice under Salt Stress.

Salt stress has the most severe impact on plant growth and development, including seed germination. However, little is known about the mechanism of NR (nitrate reductase)-associated nitric oxide (NO) regulates salt tolerance during seed germination in rice. Herein, we shown that inhibition of seed germination by salt stress was significantly impaired by sodium nitroferricyanide (SNP), a NO donor. Then a triple mutant, nr1/nr2/nr3, was generated. Results shown that germination of triple mutants were delayed and were much more sensitive to salt stress than WT plant, which can be rescued by application of SNP. qPCR analysis revealed that expressions of abscisic acid (ABA) catabolism gene, OsABA8ox1, was suppressed in triple mutants under salt stress, resulting in an elevated ABA content. Similar to SNP, application of nitrate also rescued seed germination under salt stress, which, however, was blocked in the triple mutants. Further study revealed that a nitrate responsive transcript factor, OsNLP2, was induced by salt stress, which thus up-regulates the expression of OsNRs and NR activity, resulting in promoted salt tolerance during seed germination. In addition, nitrate-mediated salt tolerance was impaired in mutant of aba8ox1, a target gene for NLP2. Transient trans-activation assays further revealed NLP2 can significantly activate the expression of OsABA8ox1 and OsNR1, suggesting that NLP2 activates expression of ABA catabolism gene directly or indirectly via NR-associated NO. Taken together, our results demonstrate that NLP2-NR associated NO was involved in salt response by increasing ABA catabolism during seed germination and highlight the importance of NO for stress tolerance of plants.

SALT AND ABA RESPONSE ERF1 improves seed germination and salt tolerance by repressing ABA signaling in rice.

Rice (Oryza sativa) germination and seedling establishment, particularly in increasingly saline soils, are critical to ensure successful crop yields. Seed vigor, which determines germination and seedling growth, is a complex trait affected by exogenous (environmental) and endogenous (hormonal) factors. Here, we used genetic and biochemical analyses to uncover the role of an APETALA2-type transcription factor, SALT AND ABA RESPONSE ERF1 (OsSAE1), as a positive regulator of seed germination and salt tolerance in rice by repressing the expression of ABSCISIC ACID-INSENSITIVE5 (OsABI5). ossae1 knockout lines exhibited delayed seed germination, enhanced sensitivity to abscisic acid (ABA) during germination and in early seedling growth, and reduced seedling salt tolerance. OsSAE1 overexpression lines exhibited the converse phenotype, with increased seed germination and salt tolerance. In vivo and in vitro assays indicated that OsSAE1 binds directly to the promoter of OsABI5, a major downstream component of the ABA signaling pathway and acts as a major regulator of seed germination and stress response. Genetic analyses revealed that OsABI5-mediated ABA signaling functions downstream of OsSAE1. This study provides important insights into OsSAE1 regulation of seed vigor and salt tolerance and facilitates the practical use of OsSAE1 in breeding salt-tolerant varieties suitable for direct seeding cultivation.

Hydrogen Peroxide Induced Antioxidant-Coupled Redox Regulation of Germination in Rice: Redox Metabolic, Transcriptomic and Proteomic Evidences

Hydrogen Peroxide Induced Antioxidant-Coupled Redox Regulation of Germination in Rice: Redox Metabolic, Transcriptomic and Proteomic Evidences

Acetic acid disturbs rice germination and post-germination under controlled conditions mimicking green mulching in flooded paddy

Cover crop use in organic rice cropping systems efficiently manages the two most limiting factors in organic agriculture - weed competition and nutrient availability. Nonetheless, cover crop biomasses on soil surfaces under the anaerobic conditions in flooded rice systems produce organic acids (mainly acetic acid) that cause early phytotoxicity to rice seedling coleoptile and roots. This study evaluated the dose-response of acetic acid on germination rates and post-germination growth traits (coleoptile, first leaf, and roots). Under controlled conditions, the seeds of three rice varieties (Sant’Andrea, Salvo, and Selenio) were immersed in acetic acid concentrations (0, 9, 18, 36, 54, and 72 ppm) for eight days. Germination results suggest that acetic acid likely scarred var. Salvo, based on a 15% faster germination rate compared to untreated controls. Across all varieties, increased acetic acid concentrations never slowed germination. During post-germination growth stages, root phytotoxicity was always more evident than shoot phytotoxicity, although the responses varied among the varieties. Root length damage appeared first at acetic acid concentrations of 36 ppm in var. Sant’Andrea and Selenio, and at 54 ppm in var. Salvo. Root length measurements provided explicit and speedy information on varietal tolerance to acetic acid and, consequently to cover crop fermentation and suggested that direct observation of root damage in paddy fields is valuable for prompt water management decisions, such as flooding interruption. Further development of this method may lead to more complete varietal screening and identification of related genetic traits responsible for tolerance. Highlights- Based on genotype, increasing acetic acid levels in flooding waters can speed rice germination.- Roots are more sensitive than shoots to acetic acid phytotoxicity during very early germination.- Early root length impairments provide information on tolerance to acetic acid phytotoxicity.- A slower germination rate may induce higher tolerance to green mulching.

Exploring the negative effects of biochars on the germination, growth, and antioxidant system of rice and corn

This study investigated the effects of biochars pyrolyzed at different temperatures on plant germination and growth and attempted to determine the mechanisms underlying those effects. The experimental results showed that phytotoxicity of biochar pyrolyzed at 500 or 800 °C was significantly higher than that of biochar pyrolyzed at 200 °C, especially at high dosages (200.0 and 300.0 g/L). However, concentrations of heavy metals and polycyclic aromatic hydrocarbon (PAHs) in biochar pyrolyzed at 500 and 800 °C were lower than those in biochar pyrolyzed at 200 °C. The inhibitory effect of aqueous biochar extract on seed germination was significantly weaker than that of biochar. Electron paramagnetic resonance (EPR) signal intensity was enhanced with increasing pyrolysis temperature, which indicates the existence of a greater number of free radicals. Furthermore, •OH and •O2− were the primary reactive oxygen species in the biochar system. It can be concluded that the phytotoxicity of biochar pyrolyzed at high temperatures (>500 °C) enables to attributing free radical-induced oxidative damage, whereas that of biochar produced at low temperatures (200 °C) results in the presence of conventional contaminants (such as heavy metals and PAHs). The information obtained in this study provides a more comprehensive understanding of the potential risk of free radicals in plant system biochar.

Preparation and Properties of Bio-Based Polyurethane Controlled Release Urea Coating with Photosensitivity.

In order to improve the photodegradation ability of fertilizer coating material and realize the sustainability of fertilizers, in this study, the commercially available photosensitive iron stearate (FeSt3) was wet-ground into submicrometer FeSt3 (SFeSt3) particles and used in preparation of a SFeSt3-modified bio-based polyurethane (PU)-coated controlled release urea (PU-SFe-CRU). The results showed that after 1 month photodegradation, the coating material had significant yellowing, the oxygen content of SFeSt3-modified PU (PU-SFe) increased by 56.89%, and its structure became more porous and looser than PU. The thermal stability of PU-SFe decreased, and more intermediate products were produced after exposure to UV light. The germination experiment showed that PU-SFe before and after photodegradation (up to 60 mg/L) had no adverse effect on the seed germination and bud growth of rice. Additionally, PU-SFe had a significantly higher Cr adsorption capacity after photodegradation due to the increase of the oxygen-containing group and specific surface. This study provides a theoretical basis for the research and development of photodegradable environment-friendly controlled release urea.

OsGAMYBL2 is required for pollen maturation and germination in rice

The reproductive development process of rice is not only important for basic developmental biology research, but also of great benefit to production practice. However, current understanding of the reproductive growth process is relatively limited, especially in the later stages of development. Here we report that OsGAMYBL2, a homologous gene of GAMYB, is required for pollen maturation and germination in rice, and that loss of function of OsGAMYBL2 leads to male sterility in rice. We generated three alleles of OsGAMYBL2 knockout mutants using CRISPR/Cas9 system, all of them lost fertility when grown in the paddy field. Semi-section and electron microscopy observations revealed that there are no visible morphological changes in the outer and inner surfaces of anther and in the surface of mature pollens between mutants and wild type. However, pollens at late developmental stages exhibited much lighter pollen viability staining and some of them shriveled. In vitro and in vivo germination experiments showed that mutant pollens fail to germinate, leading to abnormal pollen tube formation and subsequent defective pollination. Furthermore, we observed that as compared with high temperature at 30 ​°C, low-temperature at 22 ​°C affects less on osgmybl2 fertility. Collectively, we proposed that OsGAMYBL2 is likely involved in the regulation of starch accumulation during later pollen development with a thermal-sensitive way, which improves our understanding on the reproductive development in plants.

Effects of pulsed light on germination and gamma-aminobutyric acid synthesis in brown rice.

This study observed the effects of pulsed light (PL) on the germination and gamma-aminobutyric acid (GABA) production of brown rice and analyzed the correlations among glutamic acid (Glu) content, glutamate decarboxylase (GAD) activity, and GABA content in germinating brown rice. Both germination and GABA content were increased by exposure to PL, and this effect was evident when brown rice was exposed to PL immediately after being soaked. The PL group had significantly higher Glu and GABA content than the control check (CK) group which was unexposed to PL during the germination of brown rice. Glu content peaked at 18 h and GABA peaked at 24h in the PL group, which were 12 h and 6 h earlier than the CK group, respectively. GAD activity of the PL group peaked 12 h after germination, 6 h earlier than the CK group. PL exposure also increased the free amino acid content in the earliest stage of brown-rice germination. During brown-rice germination, the production of GABA is regulated by GAD activity and is significantly positively correlated with Glu content. PL treatment had a significant effect on GAD activity and Glu content during the germination process of brown rice and helped to increase its GABA content. PRACTICAL APPLICATION: This study has shown that pulsed light exposure is an efficient and stable processing method for producing brown rice with high GABA. This will provide a new direction for developing novel germination grain foods.

Seed Germination and Vigor of Four Philippine Rice Varieties as Influenced by Hydropriming and Storage at Various Durations

Rice seed germination and vigor are vital qualities to improve seedling growth and eventual yield. This study determined the effects of different hydropriming (0, 6, 12, or 18 h) and storage duration (0, 1, 2, and 3 mo) on the seed germination properties and seedling vigor of three irrigated varieties ‘Angelica’, ‘Tubigan 14’, ‘Tubigan 24’, and a rainfed variety ‘Sahod Ulan 9’. The seed quality and germination responses after hydropriming were evaluated every month during storage in ambient conditions (28 ± 2 °C; 85 ± 5% RH) for 3 mo. ‘Sahod Ulan 9’ showed tolerance to low moisture content (MC), higher germination percentage (GP) and germination index (GI), plus faster mean germination time (MGT) and days to radicle emergence (DRE); it also produced seedlings with longer shoots compared to ‘Angelica’, ‘Tubigan 14’, ‘Tubigan 24’. On the other hand, the irrigated varieties showed a higher seed vigor index (SVI) because of their high GP plus longer roots and seedlings. Hydropriming seeds for 6 or 12 h maintained a lower MC, which resulted in higher GP, GI, and SVI; fastest MGT and DRE; and longer shoot, root, and seedling. This study suggests that hydropriming rice seeds of these varieties for 6 h is sufficient to improve germination and vigor. The results suggest that hydropriming rice seeds for 6 h is sufficient to boost the rice germination and vigor of the four rice varieties tested, especially ‘Sahod Ulan 9’. Storage in ambient room conditions is suggested to be limited to only 1 mo after hydropriming as the germination responses decline thereafter. Moreover, the interaction effects of genotype, hydropriming duration, and storage time were found in GP; GI; DRE; root, shoot, and seedling lengths; and SVI.

Identification of OsPK5 involved in rice glycolytic metabolism and GA/ABA balance for improving seed germination via genome-wide association study.

Seed germination plays a pivotal role in the plant life cycle, and its precise regulatory mechanisms are not clear. In this study, 19 quantitative trait loci (QTLs) associated with rice seed germination were identified through genome-wide association studies (GWAS) of the following traits in 2016 and 2017: germination rate (GR) at 3, 5, and 7 days after imbibition (DAI) and germination index (GI). Two major stable QTLs, qSG4 and qSG11.1, were found to be associated with GR and GI over 2 continuous years. Furthermore, OsPK5, encoding a pyruvate kinase, was shown to be a crucial regulator of seed germination in rice, and might be a causal gene of the key QTL qSG11.1, on chromosome 11. Natural variation in OsPK5 function altered the activity of pyruvate kinase. The disruption of OsPK5 function resulted in slow germination and seedling growth during seed germination, blocked glycolytic metabolism, caused glucose accumulation, decreased energy levels, and affected the GA/ABA balance. Taken together, our results provide novel insights into the roles of OsPK5 in seed germination, and facilitate its application in rice breeding to improve seed vigour.

Analysis of gene expression in early seed germination of rice: landscape and genetic regulation

BackgroundSeed germination is a crucial process, which determines the initiation of seed plant life cycle. The early events during this important life cycle transition that called early seed germination is defined as initially water uptake plus radicle growing out of the covering seed layers. However, a specific genome-wide analysis of early seed germination in rice is still obscure.ResultsIn this study, the physiological characteristics of rice seed during seed germination are determined to define key points of early seed germination. Transcriptome analyses of early phase of seed germination provided deeper insight into the genetic regulation landscape. Many genes involved in starch-to-sucrose transition were differentially expressed, especially alpha-amylase 1b and beta-amylase 2, which were predominantly expressed. Differential exon usage (DEU) genes were identified, which were significantly enriched in the pathway of starch and sucrose metabolism, indicating that DEU events were critical for starch-to-sucrose transition at early seed germination. Transcription factors (TFs) were also dramatic expressed, including the abscisic acid (ABA) responsive gene, OsABI5, and gibberellic acid (GA) responsive genes, GAI. Moreover, GAI transactivated GA responsive gene, GAMYB in vivo, indicating a potential pathway involved in early seed germination process. In addition, CBL-interacting protein kinase (CIPK) genes, such as CIPK13, CIPK14 and CIPK17 were potentially interacted with other proteins, indicating its pivotal role at early seed germination.ConclusionTaken together, gene regulation of early seed germination in rice was complex and protein-to-gene or protein-to-protein interactions were indispensable.

Comparative Response of Phosphate Solubilizing Indigenous Bacillus licheniformis, Pantoea dispersa and Staphylococcus sp. From Rice Rhizosphere for Their Multifarious Growth Promoting Characteristics

Phosphorus (P), a major limiting macronutrient for plant growth and development can be made available to the plants by applying phosphate solubilizing bacteria (PSB) as bioinoculants in different cropping systems as they solubilize the inaccessible P in soil and make it available to plants in a sustainable and environment-friendly manner. The objectives of the present study were to isolate and characterize PSB from the rice rhizosphere and study their plant growth-promoting attributes in rice. Three promising isolates Bacillus licheniformis, Pantoea dispersa, and Staphylococcus sp. were selected based on qualitative and quantitative P solubilizing assay. Invitro studies were performed for their plant growth-promoting traits. Liquid Chromatography Mass Spectrometry (LCMS) analysis of the culture supernatant of the test isolates was performed to study the organic acid production for P solubilization. The bacterial strains showed positive results for indole acetic acid (IAA), 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme, and siderophore production. LCMS analysis revealed the presence of glutaric acid, propionic acid, dicarboxylic acid, and hexanoic acid which might have helped in P solubilization. Application of individual PSB and their consortium in seeds enhanced percent seed germination and seedling vigor index in rice over control. The highest percent seed germination and seedling vigor index were observed in consortium treatment. Significant enhancement in root traits like root length, root volume, root dry weight, root projected area, root tips number, root segments, root volume, and average root diameter was observed in the rice plants treated with PSB as compared to control. Our results suggest that Bacillus licheniformis, Pantoea dispersa, and Staphylococcus sp. are potent plant growth-promoting bacteria and could be implemented as a low-cost bio-inoculant in the rice agriculture system.

Effect of static magnetic field treatment on the germination of brown rice: Changes in α-amylase activity and structural and functional properties in starch

The study aimed to explore the stimulating effect of static magnetic field (SMF) treatment on germinated brown rice (GBR) by monitoring changes in α-amylase activity and structural and functional properties of starch. Brown rice was exposed to SMF (10 mT, 60 min, 25 °C) and then germinated for 0 h −72 h at 30 °C. Compared with the control, SMF treatment improved α-amylase activity (15.2%), leading to the hydrolysis of starch into reducing sugar (8.2%) and increasing the germination rate (9.7% −158.8%), shoot length (9.1% −87.3%), root length (19.2% −110.0%), and fresh weight (0.9% −16.5%). In view of the properties of starch, SMF treatment also altered the surface microstructure, induced partial losses of birefringence, exerted no significant effect on the crystalline type, slightly increased the gelatinization temperatures, and significantly decreased the peak viscosity. This study suggested that SMF could serve as a prospective technique for GBR products processing.

Cereal Germination under Low Oxygen: Molecular Processes.

Cereal crops can differ greatly in tolerance to oxygen shortage under germination and seedling establishment. Rice is able to germinate and elongate the coleoptile under submergence and anoxia. This capacity has been attributed to the successful use of starchy reserves through a molecular pathway activated by sugar starvation and low oxygen. This pathway culminates with the expression of α-amylases to provide sugars that fuel the sink organs. On the contrary, barley and wheat are unable to germinate under anoxia. The sensitivity of barley and wheat is likely due to the incapacity to use starch during germination. This review highlights what is currently known about the molecular mechanisms associated with cereal germination and seedling establishment under oxygen shortage with a special focus on barley and rice. Insights into the molecular mechanisms that support rice germination under low oxygen and into those that are associated with barley sensitivity may be of help for genetic improvement programs.

Seed Treatment with Iron Chlorine E6 Enhances Germination and Seedling Growth of Rice

Iron chlorine e6 (ICE6), also known as iron dihydroporphine, is a new type natural plant growth regulator, which can improve some crops growth. At present, the effects of ICE6 on rice are still unclear. Therefore, it is of great significance to study the effect of ICE6 on rice growth. In this study, the effect of seed treatment with ICE6 on rice germination and seedling growth was evaluated. Rice seeds were soaked with the gradient concentration and gradient time of ICE6, respectively, and then the germination rate, growth indexes and chlorophyll content of rice were determined. The results showed seed soaking with ICE6 could improve rice seed germination, promote seedling growth and increase the chlorophyll content in plants, exhibiting a better growth promoting effect. The optimum soaking condition was 100–200 mg/L (concentration) and 24–48 h (time). The field experiment further verified the growth regulating effect of ICE6 priming on rice seedlings. After seed priming with ICE6, seed vigor became higher, and the activities of α-amylase and protease in germinating seeds increased. The increase of seed vigor might be an important reason that ICE6 improved the germination and seedling growth. In addition, we also found ICE6 treatment could enhance the regeneration ability of seedlings. This work demonstrated the germination and growth promoting effect of ICE6 on rice, and revealed its application potential in rice production. This seed priming technique was of great promotional value in the field.

OsWRKY53 Promotes Abscisic Acid Accumulation to Accelerate Leaf Senescence and Inhibit Seed Germination by Downregulating Abscisic Acid Catabolic Genes in Rice.

Abscisic acid (ABA) largely promotes leaf senescence and inhibits seed germination in plants. Endogenous ABA content is finely tuned by many transcription factors. In this study, we showed that OsWRKY53 is a positive regulator of leaf senescence and a negative regulator of seed germination in rice. OsWRKY53 expression was induced in leaves under aging, dark, and ABA treatment. The OsWRKY53-overexpressing (OsWRKY53-oe) plants showed early yellowing leaves, while the OsWRKY53 (oswrky53) knockout mutants maintained green leaves than the wild type under natural, dark-induced, and ABA-induced senescence conditions. Transcriptional analysis revealed that ABA catabolic genes, namely, OsABA8ox1 and OsABA8ox2, two key genes participating in ABA catabolism harboring ABA 8′-hydroxylase activity, were markedly downregulated in OsWRKY53-oe leaves. Chromatin immunoprecipitation and protoplast transient assays revealed that OsWRKY53 directly bound to the promoters of OsABA8ox1 and OsABA8ox2 to repress their transcription, resulting in elevated endogenous ABA contents that promoted premature leaf senescence in the OsWRKY53-oe plants. It indicates that OsWRKY53 is a positive regulator through regulating ABA accumulation to promote leaf senescence. In addition, accumulated ABA simultaneously inhibited seed germination and post-germination growth in OsWRKY53-oe plants. Taken together, OsWRKY53 suppresses the transcript of ABA catabolic genes to promote ABA accumulation to modulate ABA-induced leaf senescence and ABA-mediated inhibition of seed germination.

Comparative transcriptome analysis of the cold resistance of the sterile rice line 33S.

Rice (Oryza sativa L.) is one of the most important species for food production worldwide. Low temperature is a major abiotic factor that affects rice germination and reproduction. Here, the underlying regulatory mechanism in seedlings of a TGMS variety (33S) and a cold-sensitive variety (Nipponbare) was investigated by comparative transcriptome. There were 795 differentially expressed genes (DEGs) identified only in cold-treated 33S, suggesting that 33S had a unique cold-resistance system. Functional and enrichment analysis of these DEGs revealed that, in 33S, several metabolic pathways, such as photosynthesis, amino acid metabolism, secondary metabolite biosynthesis, were significantly repressed. Moreover, pathways related to growth and development, including starch and sucrose metabolism, and DNA biosynthesis and damage response/repair, were significantly enhanced. The expression of genes related to nutrient reserve activity were significantly up-regulated in 33S. Finally, three NAC and several ERF transcription factors were predicted to be important in this transcriptional reprogramming. This present work provides valuable information for future investigations of low-temperature response mechanisms and genetic improvement of cold-tolerant rice seedlings.