Rice Plant Height Research Articles

Effective antioxidant defense prevents nitro-oxidative stress under arsenic toxicity: A study in rice genotypes of eastern Indo-Gangetic plains

Arsenic (As) toxicity in humans and animals has become a major concern in the last few decades. Rice growing on As-contaminated soil is the principal dietary source of As that poses a significant health hazards to rice patrons, making it a global issue of concern to take necessary steps to counteract the problem. Eastern Indo-Gangetic plains (EIGP) is one of the world’s hotspot for As pollution. Arsenic contaminated irrigation is the principal reason for elevated As levels in the agricultural fields of EIGP, which affects rice productivity. The present study intended to explore the influences of As toxicity (arsenite and arsenate) on the morpho-physiology, ionomics, and biochemical performances of 18 rice genotypes of EIGP at the seedling stage. Arsenic exposure negatively affected plant height, root length, and biomass in rice. It also induced membrane degradation thereby, decreasing total chlorophyll content. It also impaired the nutrient uptake and root-to-shoot translocation abilities of plants. Arsenic toxicity led to the accumulation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) consequently, inducing nitro-oxidative stress in rice. Arsenic tolerance in rice was related to the antioxidant defense system that decreased the malondialdehyde (MDA) content and improved the membrane stability thereby, sustaining plant growth. Additionally, proline facilitated ROS eradication conferring protection against the As-induced nitro-oxidative stress. In this study genotypic variation was obvious in all traits associated with As toxicity. Among the rice genotypes studied, Sahbhagi Dhan and Sabour Ardhjal displayed considerably higher As tolerance with sustainable plant growth, membrane stability, nutrient homeostasis, enhanced antioxidant enzyme activities, lower ROS/RNS and MDA accumulations under different As treatments. Overall, the study revealed the association between proteomic and ionomic profiles in rice to understand the potential adaptive mechanisms in plants under As toxicity.

Effects of stabilizing materials on soil Cd bioavailability, uptake, transport, and rice growth

Cadmium, a widespread toxic heavy metal in farmland soils, is harmful to human health. A field experiment was conducted to investigate the effects of biochar and biochar-based fertilizers on soil pH, organic matter, and available Cd, as well as rice Cd uptake and translocation. The results showed that rice biomass was significantly increased after both the application of biochar and high rate of biochar-based fertilizers at the tillering stage. The biomass and plant height of rice were improved at filling and maturity stages. Soil pH was significantly increased with the application of biochar but not with the biochar-based fertilizer. The amendments of biochar and biochar-based fertilizers had no significant (p < 0.05) influence on soil organic matter content. The concentration of available Cd in soil and the concentration of Cd in rice were decreased with the application of different amounts of biochar and biochar-based fertilizers in the mature stage. However, this effect was much greater under biochar amendment. Compared to the control, the concentration of available Cd in soil was reduced by 33.09% with the low application rate of biochar, while that was reduced by 18.06% with the high application rate of biochar. The lowest bioaccumulation factor was due to the high concentration of biochar and biochar-based fertilizers. It is concluded that biochar and biochar-based fertilizers particularly at a high addition rate are appropriate for decreasing Cd mobility and improve soil quality for contaminated paddy soils. The study showed a method for the safe production of rice in Cd-polluted farmlands by using a high application rate of biochar or carbon-based fertilizers.

OsDREB2B, an AP2/ERF transcription factor, negatively regulates plant height by conferring GA metabolism in rice.

The AP2/ERF family is a large group of plant-specific transcription factors that play an important role in many biological processes, such as growth, development, and abiotic stress responses. OsDREB2B, a dehydration responsive factor (DRE/CRT) in the DREB subgroup of the AP2/ERF family, is associated with abiotic stress responses, such as cold, drought, salt, and heat stress, in Arabidopsis or rice. However, its role in regulating plant growth and development in rice is unclear. In this study, we reported a new function of OsDREB2B, which negatively regulates plant height in rice. Compared with wild type (WT), OsDREB2B-overexpressing (OE) rice exhibited dwarf phenotypes, such as reduction in plant height, internode length, and seed length, as well as grain yield, while the knockout mutants developed by CRISPR/Cas9 technology exhibited similar phenotypes. Spatial expression analysis revealed that OsDREB2B was highly expressed in the leaf sheaths. Under exogenous GA3 application, OsDREB2B expression was induced, and the length of the second leaf sheath of the OsDREB2B-OE lines recovered to that of the WT. OsDREB2B localized to the nucleus of the rice protoplast acted as a transcription activator and upregulated OsAP2-39 by directly binding to its promoter. OsDREB2B-OE lines reduced endogenous bioactive GA levels by downregulating seven GA biosynthesis genes and upregulating eight GA deactivation genes but not GA signaling genes. The yeast two-hybrid assay and bimolecular fluorescence complementation assay showed that OsDREB2B interacted with OsWRKY21. In summary, our study suggests that OsDREB2B plays a negative role in rice growth and development by regulating GA metabolic gene expression, which is mediated by OsAP2-39 and OsWRKY21, thereby reducing GA content and rice plant height.

OsHLS1 regulates plant height and development by controlling active gibberellin accumulation in rice (Oryza sativa L.)

In this study, we identified a gene related to plant height, leaf, and premature senescence in rice, and named it OsHLS1. Through bioinformatics analysis, it was found that this gene belongs to a new gene family-HLS family, and this gene family exists widely in higher plants. Expression of OsHLS1 was significantly brought about by gibberellin (GA). Subcellular localization showed that OsHLS1 was located in the nucleus. oshls1–3 displayed a GA-deficient phenotype, with dwarf plants. In addition, oshls1–3 also showed premature senescence, shorter and narrower leaves, and pollen abortion. Exogenous GA3 can restore the plant height of oshls1–3. Histomorphological analysis showed that the gene affected the progress of internode cells in the first and third nodes under the rice panicle. Through the verification of the homologous gene AT4G25690 in Arabidopsis, it was found that the mutant at4g25690 lines also showed plant dwarfing, premature senescence, and shortening and narrowing of leaves and pollen abortion. OsHLS1 affected the expression levels of genes involved in the GA metabolic pathway and affected the content of active GA, thereby regulating plant height development in rice. In conclusion, we suggest that OsHLS1 regulates plant height and development by controlling the accumulation of active gibberellins in rice.

CRY2 gene of rice (Oryza sativa subsp. indica) encodes a blue light sensory receptor involved in regulating flowering, plant height and partial photomorphogenesis in dark.

OsiCRY2 is involved in light-regulated plant development and plays a role in regulating photomorphogenesis, plant height, flowering and most strikingly partial photomorphogenesis in dark. Cryptochrome 2 (CRY2), the blue/UV-A light photoreceptor in plants, has been reported to regulate photoperiod-dependent flowering and seedling photomorphogenesis (under low-intensity light). Among monocots, CRY2 has been reported from japonica rice, wheat, sorghum and barley. The two sub-species of rice, indica and japonica, exhibit a high degree of genetic variation and morphological and physiological differences. This article describes the characterization of CRY2 of indica rice (OsiCRY2). While the transcript levels of OsiCRY2 did not change significantly under blue light, its protein levels were found to decline with increased time duration under blue light. For phenotypic characterization, OsiCRY2 over-expression (OX) transgenics were generated in Oryza sativa Pusa Sugandh 2 (PS2) cultivar, a highly scented Basmati cultivar. The OsiCRY2OX transgenics displayed shorter coleoptiles and dwarfism than wild-type under blue light, white, and far-red light. Interestingly, even the dark-grown transgenics were shorter, concomitant with higher OsiCRY2 protein levels in transgenics than wild-type. Histological analysis revealed that the decrease in the length of the seedlings was due to a decrease in the length of the epidermal cells. The fully mature rice transgenics were shorter than the untransformed plants but flowered at the same time as wild-type. However, the OsiCRY2 Arabidopsis over-expressors exhibited early flowering by 10-15days, indicating the potential and conservation of function of OsiCRY2. The whole-genome transcriptome profiling of rice transgenics revealed the differential up-regulation of several light-regulated genes in dark-grown coleoptiles. These data provide evidence that OsiCRY2 regulates photomorphogenesis, plant height, and flowering in indica rice.

CRISPR/Cas9-targeted mutagenesis of a representative member of a novel PR10/Bet v1-like protein subfamily significantly reduces rice plant height and defense against Meloidogyne graminicola

Plant PR10/Bet v1-like proteins are involved in defense against microbial pathogens, however, whether they participate in host defense against plant-parasitic animals including nematodes remains unknown. Here, according to the phylogeny, sequence-similarity, and secondary structure analyses, we found that the rice OsBet v1 protein and its homologs constitute a new subfamily of PR10/Bet v1-like protein. Reverse transcription-quantitative PCR assay showed that OsBet v1 was highly expressed in rice roots and induced by Meloidogyne graminicola infection. Using a transient expression assay in rice protoplasts, we demonstrated that OsBet v1 was localized in the cytoplasm and nucleus. Furthermore, CRISPR/Cas9-targeted mutagenesis of OsBet v1 significantly increased rice susceptibility to M. graminicola, but reduced rice plant height. In addition, the expression levels of two peroxidase genes (peroxidase 5 and peroxidase 56) were significantly down-regulated in OsBet v1 knockout mutants compared with those in wild-type rice plants. Taken together, this study identified a new PR10/Bet v1-like protein subfamily in plant and revealed the involvement of OsBet v1, a representative member of the subfamily, in rice growth and defense against M. graminicola. This provides a new insight into the role of plant PR10/Bet v1-like proteins in plant–nematode interactions.

The combined use of a plant growth promoting Bacillus sp. strain and GABA promotes the growth of rice under salt stress by regulating antioxidant enzyme system, enhancing photosynthesis and improving soil enzyme activities

Salt stress poses a global challenge for agriculture, crop growth, and food production. In this study, a strain of rhizobacteria with both plant growth-promoting (PGP) traits and salt tolerance was isolated. The strain was identified as Bacillus pumilus via 16 S rDNA sequencing and was named B. pumilus JIZ13. This strain had the potential to solubilize phosphates and produce 1-aminocyclopropane-1-carboxylic acid deaminase, siderophores, and indole-3-acetic acid. After 35 days of salt stress exposure, the root length, plant height, dry weight, fresh weight, and relative water content of rice plants inoculated with strain JIZ13 were significantly higher than those without inoculation. Interestingly, the PGP properties of strain JIZ13 were significantly improved by the exogenous addition of gamma-aminobutyric acid (GABA). Moreover, GABA also enhanced the growth and development of rice plants under salt stress by providing substrates for the tricarboxylic acid cycle. Furthermore, the synergistic roles of GABA and strain JIZ13 in mitigating the damage caused by salt stress in rice plants was investigated. The results showed that the co-application of GABA and JIZ13 significantly increased photosynthetic efficiency, chlorophyll accumulation, antioxidant levels, levels of osmotic adjustment substances, and biomass of rice under salinity stress. In addition, the activities of urease, protease, invertase, and catalase enzymes in soil significantly improved under the combination of strain JIZ13 and GABA and increased by 39.65%, 36.88%, 70.21%, and 65.23%, respectively, compared to those without rhizobacterial and GABA additions. The enhancement of these four soil enzyme activities might thus improve soil quality and increase root elongation and biomass in rice plants. The results of this study provide the first evidence that PGP-rhizobacterial strain JIZ13 along with GABA can attenuate the negative effects of salt stress in rice plants.

Mapping and Validation of qHD7b: Major Heading-Date QTL Functions Mainly under Long-Day Conditions.

Heading date (HD) is one of the agronomic traits that influence maturity, regional adaptability, and grain yield. The present study was a follow-up of a previous quantitative trait loci (QTL) mapping study conducted on three populations, which uncovered a total of 62 QTLs associated with 10 agronomic traits. Two of the QTLs for HD on chromosome 7 (qHD7a and qHD7b) had a common flanking marker (RM3670) that may be due to tight linkage, and/or weakness of the statistical method. The objectives of the present study were to map QTLs associated with HD in a set of 76 chromosome segment substitution lines (CSSLs), fine map and validate one of the QTLs (qHD7b) using 2997 BC5F2:3 plants, and identify candidate genes using sequencing and expression analysis. Using the CSSLs genotyped with 120 markers and evaluated under two short-day and two long-day growing conditions, we uncovered a total of fourteen QTLs (qHD2a, qHD4a, qHD4b, qHD5a, qHD6a, qHD6b, qHD7b, qHD7c, qHD8a, qHD10a, qHD10b, qHD11a, qHD12a, and qHD12b). However, only qHD6a and qHD7b were consistently detected in all four environments. The phenotypic variance explained by qHD6a and qHD7b varied from 10.1% to 36.1% (mean 23.1%) and from 8.1% to 32.8% (mean 20.5%), respectively. One of the CSSL lines (CSSL52), which harbored a segment from the early heading XieqingzaoB (XQZB) parent at the qHD7b locus, was then used to develop a BC5F2:3 population for fine mapping and validation. Using a backcross population evaluated for four seasons under different day lengths and temperatures, the qHD7b interval was delimited to a 912.7-kb region, which is located between RM5436 and RM5499. Sequencing and expression analysis revealed a total of 29 candidate genes, of which Ghd7 (Os07g0261200) is a well-known gene that affects heading date, plant height, and grain yield in rice. The ghd7 mutants generated through CRISPR/Cas9 gene editing exhibited early heading. Taken together, the results from both the previous and present study revealed a consistent QTL for heading date on chromosome 7, which coincided not only with the physical position of a known gene, but also with two major effect QTLs that controlled the stigma exertion rate and the number of spikelets in rice. The results provide contributions to the broader adaptability of marker-assisted breeding to develop high-yield rice varieties.

Controlling the lodging risk of rice based on a plant height dynamic model

BackgroundRice is a key global food crop. Rice lodging causes a reduction in plant height and crop yield, and rice is prone to lodging in the late growth stage because of panicle initiation. We used two water irrigation modes and four fertilizer application intervals to investigate the relationship between lodging and various cultivation conditions over 2 years.ResultsPlant height data were collected and combined with aerial images, revealing that rice lodging was closely related to the nitrogen fertilizer content. The aerial images demonstrated that lodging mainly occurred in the fields treated with a high-nitrogen fertilizer, and analysis of variance revealed that plant height was signifi-cantly affected by nitrogen fertilizer. These results demonstrated that rice plant height in the booting stage was significantly positively correlated with the lodging results (r = 0.67) and nega-tively correlated with yield (r = − 0.46). If the rice plant height in the booting stage exceeded 70.7 cm and nitrogen fertilizer was continuously applied, according to the predicted growing curve of plant height, the plant would be at risk of lodging. Results showed more rainfall accumulated in the later stage of rice growth accompanied by strong instantaneous gusts, the risk of lodging in-creased.ConclusionThe results provide predictions that can be applied in intelligent production and lodging risk management, and they form the basis of cultivation management and response policies for each growth period.

Dynamic Effect of Organic Fertilizer Application on Rice Growth, Soil Physicochemical Properties and Cd Activity Exposed to Excess Cd.

To investigate the dynamic effects of organic fertilizer application on the agronomic traits of rice (Oryza sativa L.), soil physicochemical properties and soil Cd activity under excess cadmium (Cd) exposure, this study was conducted to simulate a paddy system under different organic fertilizer application rates using exogenous spiked Cd soil as the test soil and conducting a rice pot experiment. The obtained results showed that the application of organic fertilizer increased the number of rice tillers, rice plant height, total grain number and total grain weight at maturity in all treated soils, while it decreased the concentration of Cd in brown rice. The application of organic fertilizer increased the organic matter (OM), redox potential and electrical conductivity of all treated soils but decreased the pH and TCLP-extractable Cd of all treated soils. There was a significant or highly significant negative correlation (p < 0.05 or p < 0.01) between soil TCLP-extractable Cd and soil OM throughout the experimental period, implying that soil OM may be an important factor influencing the changes in Cd activity in soil. In addition, our experiment also examined in detail the dynamic change process of the abovementioned indicators throughout the experimental period and observed that the dynamic change process of soil Cd activity could be described as a trend of first decreasing and then gradually increasing throughout the rice reproductive period.

Foliar application of procyanidins enhanced the biosynthesis of 2-acetyl-1-pyrroline in aromatic rice (Oryza sativa L.)

BackgroundProcyanidins is a polyphenolic compound with multiple properties. However, the application of exogenous procyanidins in crops has not been reported. Aromatic rice is a high-quality rice with a special aroma and popular with consumers. The 2-acetyl-1-pyrroline (2-AP) is a key compound of aromatic rice aroma. In the current study, aromatic rice plants were sprayed with procyanidins solutions at 0.25 (Pr0.25), 0.50 (Pr0.50), 1.00 (Pr1.00), 2.00 (Pr2.00) g L−1, respectively and treatment sprayed with distilled water was taken as control (CK). The effects of exogenous procyanidins on growth and 2-AP biosynthesis of aromatic rice plants were explored.ResultsCompared with CK, Pr1.00 and Pr2.00 treatments significantly increased 2-AP content by 16.67% and 37.68%, respectively. Higher proline, 1-pyrroline-5-carboxylic acid (P5C), 1-pyrroline, methylglyoxal contents, and lower γ- aminobutyric acid (GABA) content were recorded in Pr1.00 and Pr2.00 treatments than CK. Compared with CK, Pr1.00 and Pr2.00 treatments significantly improved the activities of P5CS and OAT and diminished the activity of BADH. Furthermore, compared with CK, Pr1.00 and Pr2.00 treatments significantly up-regulated the transcript levels of P5CS2, P5CR, OAT, DAO4 and down-regulated the transcript levels of BADH2. Exogenous procyanidins had no substantial effects on plant height, stem diameter, fresh weight, and dry weight of aromatic rice plants.ConclusionsIn conclusion, our findings reported the increment of 2-AP content in aromatic rice under exogenous procyanidins. Our results indicated that the application of exogenous procyanidins enhanced 2-AP biosynthesis by improving proline biosynthesis and inhibiting GABA formation.

Growth And Production Of Several Rice Varieties With The Biochar From Different Sources Of Materials

This research will be carried out in the experimental land of the Tanjung Morawa Seed Center, Lubuk Pakam District, Deli Serdang Regency. The purpose of this research is to find out how the growth and production of several varieties of irrigated rice with biochar from different source. The experimental design used in this study was a split plot design with 2 factors. The first factor is: The provision of various sources of biochar with 5 levels of treatment: No biochar, rice husk biochar, coconut shell biochar, oil palm empty bunch biochar and jengkol skin biochar. The second factor was: Ciherang, Hipa 19, Inpari 33. Parameters observed were plant height (cm), number of panicles, weight of 1000 grains (g and soil analysis. The results showed that the use of several varieties of lowland rice on the growth and production of irrigated rice had a significant effect on the height of rice plants from 6-9 WAP. The use of several varieties of rice such as Ciherang, Hipa 10 and Inpari 33 varieties showed differences in plant height starting at the age of 6 WAP. The results of the final analysis of paddy fields after being given biochar treatment experienced an increase in nutrients such as N-total, P, K and organic C in all treatments.

OsNPF3.1, a member of the NRT1/PTR family, increases nitrogen use efficiency and biomass production in rice

The overuse of nitrogen (N) fertilizer in fields has increased production costs and raised environmental concerns. Increasing the N use efficiency (NUE) of rice varieties is crucial for sustainable agriculture. Here we report the cloning and characterization of OsNPF3.1, a gene that controls rice NUE. An amino acid mutation in the OsNPF3.1 coding region caused different NUEs in wild and cultivated rice. OsNPF3.1, which is expressed mainly in the aerial parts of rice, also affects rice plant height, heading date, and thousand-grain weight. The OsNPF3.1 protein is located in the plasma membrane. When OsNPF3.1 was subjected to artificial selection, two naturally varying loci were associated with NUE, of which OsNPF3.1Chr6_8741040 differed between indica and japonica rice. OsNPF3.1 can be used as a new target gene for breeding rice varieties with high NUE.

Natural variation of the BRD2 allele affects plant height and grain size in rice.

The zqdm1 identified from a rice mutant is a novel allele of BRD2 and is responsible for regulating rice plant height, grain size and appearance, which has possibilities on improving rice quality. Plant height is an important agronomic trait related to rice yield, and grain size directly determines grain yield in rice (Oryza sativa L.). With the development of molecular biotechnology and genome sequencing technology, more and more key genes associated with plant height and grain size have been cloned and identified in recent years. This study identified the zqdm1 gene from a mutant with reduced plant height and grain size. The zqdm1 gene was revealed to be a new allele of BRASSINOSTEROID DEFICIENT DWARF 2 (BRD2), encoding a FAD-linked oxidoreductase protein involved in the brassinosteroid (BR) biosynthesis pathway, and regulates plant height by reducing cell number of longitudinal sections of the internode and regulates grain size by altering cell expansion. A 369-bp DNA fragment was found inserted at the first exon, resulting in protein-coding termination. This mutation has not been discovered in previous studies. Complementation tests have confirmed that 369-bp insertion in BRD2 was responsible for the plant height and grain size changing in the zqdm1 mutant. Over-expression of BRD2 driven by different promoters into indica rice variety Jiafuzhan (JFZ) results in slender grains, suggesting its function on regulating grain shape. In summary, the current study has identified a new BRD2 allele, which facilitated the further research on the molecular mechanism of this gene on regulating growth and development.

Long-Term Effects of Biochar Application With Reduced Chemical Fertilizer on Paddy Soil Properties and japonica Rice Production System

To clarify the effects of co-application of rice-straw biochar and different chemical fertilizer doses on paddy soil properties and japonica rice production in Northeast China, a located-field experiment was adopted for 5 years. The treatments included fertilization (F, no biochar, control) and rice-straw biochar (7.5 t ha−1) combined with different chemical fertilizer doses (100, 80, and 60% that of F) set as CF, CF1, and CF2, respectively. The results showed that the co-application of biochar and chemical fertilizers after 5 years reduced soil bulk density, increased soil total and capillary porosity, changed the soil solid–liquid–gas ratio (increased the liquid and air ratios and decreased the solid ratio), and increased soil macroaggregates (&amp;gt;0.25 mm) and aggregate stability, which enhanced the soil’s physical properties. Furthermore, the co-application improved soil pH and soil enzyme activity (urease, sucrase, and catalase) and had a significant effect on promoting SOM. The soil total N, P, and K of CF and CF1, were 23.48, %, 47.28%, and 26.59% and 9.47%, 43.98%, and 27.87% higher than those of the control, respectively. The soil available nutrients (N, P, and K) increased in the co-application treatment, shown as the nitrogen was promoted higher in the early growth of rice, while phosphorus and potassium were exhibited greater in the late growth. With the soil amendment, the co-application increased the rice plant height and dry matter accumulation, and the CF and CF1 increased yields by 5.78 and 2.41%, respectively, by increasing the rice effective panicles, grains per panicle, and seed-setting rate. The co-application of biochar and chemical fertilizers could significantly amend soil properties and reduce chemical fertilizer use to ensure rice–grain output, which has an important significance for enhancing sustainable soil and crop productivity.

Combining Proteomics and Metabolomics to Analyze the Effects of Spaceflight on Rice Progeny.

Spaceflight is a special abiotic stress, the biological effect mechanism of which on contemporary rice has been clarified, However, its effect on offspring rice was still unclear. In order to understand the response mechanism of F2 generation plants to space flight, this study used SJ-10 recoverable satellite to carry DN423 rice seeds for 12.5 days in orbit flight. After returning to the ground, the plants were then planted to F2 generation to explore the biological effect mechanism. Our research showed that in the F2 generation of TLS, the rice plant height of the space flight group increased by 33.8%, the ear length and thousand-grain weight decreased by 9.7 and 4.6%, respectively, and the grain number per panicle increased by 6.5%. Moreover, related proteins that control changes in agronomic traits have been identified. The changes of MDA, H2O2, soluble sugar, electron leakage and antioxidant enzyme activity confirmed the stress response in F2 generation plants. ITRAQ and LC-MS technology were used to reveal the change pattern of protein levels and metabolite levels in F2 generation plants, 389 and 405 proteins were identified as differentially abundant proteins in TLS and TS, respectively. In addition, there were 124 and 125 metabolites that changed during these two periods. The proteome and metabolome result further confirmed that the F2 generation plants still retained the memory of space flight stress, and retained the memory of space flight stress through genome instability. Oxidative stress signals activated sugar signals to rebuild metabolic networks to adapt to space flight stress. The reconstruction of energy metabolism, amino acid metabolism, phenylalanine metabolism, and flavonoid metabolism played an important role in the process of adapting to space flight stress. The results of this study broaden the perspective of space biological effects and provide a basis for studying the effects of abiotic stress on plant progeny.

An effective planting model to decrease cadmium accumulation in rice grains and plants: Intercropping rice with wetland plants

Cadmium (Cd) pollution affects plant growth and poses a serious threat to food safety and human health. Cadmium-contaminated rice is assumed to be the main source of Cd exposure to humans, with grave health risks. Phytoremediation is an efficient, cost-effective, and eco-friendly approach to minimizing Cd accumulation in rice. However, research on the effect of rice intercropping with wetland plants that exhibit great capacity for phytoremediation in decreasing Cd concentrations in paddies is limited. A pot experiment in glasshouse was conducted to evaluate the effects of rice intercropping with two wetland plants ( Pontederia cordata and Canna indica ) under different Cd levels (0, 1, 10, and 25 mg kg −1 ) on rice growth and Cd accumulation and translocation. The results showed that intercropping with the two wetland plants significantly improved the plant height, tiller, and biomass of rice but reduced the bioconcentration factors (BCFs) and Cd concentration in rice and wetland plants. Compared with rice monocropping, the BCF of rice grain in treatments with 25 mg kg −1 Cd was significantly decreased by 54.39% and 59.65% in rice intercropped with C . indica (RC) and rice intercropped with P. cordata (RP), respectively. In addition, intercropping inhibited the increase in BCFs in rice and wetland plants under increasing soil Cd content. In conclusion, the systems of rice intercropping with P. cordata and C . indica can be considered two new and effective approaches for ameliorating Cd pollution in paddies, as well as minimizing Cd accumulation in rice and improving food safety. Of the two intercropping systems, rice intercropping with P. cordata performed better than intercropping with C . indica.

OsFBK4, a novel GA insensitive gene positively regulates plant height in rice (Oryza Sativa L.)

Semi-dwarf is one of the most valuable agronomic characteristics for rice improvement programs because it affects lodging resistance and grain yield. In the present study, a semi-dwarf mutant, RE9586 , exhibits reduced plant height, panicle length and decreased grain yield. Scanning electron microscopic observation results showed that the longitudinal length of the uppermost internode of RE9586 significantly reduced, resulting in a semi-dwarf phenotype. Employing a MutMap-based strategy, LOC_Os02g11790 was preliminarily identified as the candidate gene, which encoded the F-box domain and kelch repeat-containing protein ( OsFBK4 ). A point mutation in the 3rd exon of OsFBK4 resulted in an amino acid change of 414 R→G that was subsequently confirmed by linkage analysis. Real time-PCR showed the OsFBK4 gene was predominantly expressed in the internode. The knockout lines of OsFBK4 by CRISPR/Cas9 showed a short plant height, while OsFBK4 overexpression lines recovered the phenotype of plant height. We have also demonstrated that the expressions of GA-signaling genes such as SRL1 , CIGR , GID1 , GID2 , D1 , and SPY showed clear differences in which SRL1 was down regulated, while other genes were up-regulated in RE9586 mutant. GA biosynthesis genes, OsKAO , OsGA3ox2 , and OsGA2ox2 , also displayed apparent differences in expression level. In addition, the OsFBK4 protein probably localized to the nucleus and plasma membrane. In conclusion, OsFBK4 regulates plant height involving in GA signaling, providing further insights into the mechanisms underlying the regulation of plant height in rice.

Fine Mapping and Cloning of a Major QTL qph12, Which Simultaneously Affects the Plant Height, Panicle Length, Spikelet Number and Yield in Rice (Oryza sativa L.).

Plant height is one of the most important agronomical traits in rice (Oryza sativa L.). Introducing the semidwarf rice in the 1960s significantly enhanced the rice yield potential in Asia. Implementing near-isogenic lines (NILs) is the most powerful tool for the identification and fine mapping of quantitative trait loci (QTLs). In this study, 176 NILs were produced from the crossing and back-crossing of two rice cultivars. Specifically, the indica rice cultivar Jiafuzhan served as a recipient, and the restorer japonica cultivar Hui1586 served as a donor. Using the 176 NILs, we identified a novel major QTL for reduced plant height in the NIL36 line. The qph12 QTL was mapped to a 31 kb genomic region between the indel markers Indel12-29 and Indel12-31. The rice genome annotation indicated the presence of three candidate genes in this genomic region. Through gene prediction and cDNA sequencing, we confirmed that LOC_Os12g40890 (qPH12) is the target gene in the NIL36 line. Further analysis showed that the qph12 QTL is caused by a 1 bp deletion in the first exon that resulted in premature termination of the qPH12. Knockout experiments showed that the qph12 QTL is responsible for the reduced plant height phenotype of the NIL36 line. Although the qph12 gene from the NIL36 line showed a shorter panicle length, fewer spikelets per panicle and a lower plant grain yield, the plant also exhibited a lower plant height. Taken together, our results revealed that the qph12 have good specific application prospects in future rice breeding.

The miR528-D3 Module Regulates Plant Height in Rice by Modulating the Gibberellin and Abscisic Acid Metabolisms

Plant height, as one of the important agronomic traits of rice, is closely related to yield. In recent years, plant height-related genes have been characterized and identified, among which the DWARF3 (D3) gene is one of the target genes of miR528, and regulates rice plant height and tillering mainly by affecting strigolactone (SL) signal transduction. However, it remains unknown whether the miR528 and D3 interaction functions in controlling plant height, and the underlying regulatory mechanism in rice. In this study, we found that the plant height, internode length, and cell length of internodes of d3 mutants and miR528-overexpressing (OE-miR528) lines were greatly shorter than WT, D3-overexpressing (OE-D3), and miR528 target mimicry (OE-MIM528) transgenic plants. Knockout of D3 gene (d3 mutants) or miR528-overexpressing (OE-miR528) triggers a substantial reduction of gibberellin (GA) content, but a significant increase of abscisic acid (ABA) accumulation than in WT. The d3 and OE-miR528 transgenic plants were much more sensitive to GA, but less sensitive to ABA than WT. Moreover, the expression level of GA biosynthesis-related key genes, including OsCPS1, OsCPS2, OsKO2 and OsKAO was remarkably higher in OE-D3 plants, while the NECD2 expression, a key gene involved in ABA biosynthesis, was significantly higher in d3 mutants than in WT and OE-D3 plants. The results indicate that the miR528-D3 module negatively regulates plant height in rice by modulating the GA and ABA homeostasis, thereby further affecting the elongation of internodes, and resulting in lower plant height, which adds a new regulatory role to the D3-mediated plant height controlling in rice.