There is still much to learn with respect to the potential for microplastics (MPs) to interact with environmental toxins and biota. In the present study, we investigated the effect of MPs on the toxicity of copper (Cu) to rice seeds (Oryza sativa L.). The 7-day median effective concentration (EC50) value of MPs on rice seed germination was 864 mg/L (95% confidence interval [CI] 839 to 897 mg/L). We found that MPs slightly reduced Cu toxicity to rice seeds. The 7-day EC50 of Cu on rice seed germination increased from 7.29 mg/L (95% CI 7.10-7.52 mg/L) to 7.93 mg/L (95% CI 7.58-8.08 mg/L) in the presence of 20 mg/L MPs. We examined this toxicity reduction phenomenon by investigating the role of MPs in the process of Cu transport, Cu accumulation, and metabolic responses. Further investigation found that the MPs used in the present study hardly adsorbed Cu, but these MPs accumulated on the coats of rice seeds and significantly reduced Cu accumulation in rice seedlings. When Cu concentration was 10 mg/L, the presence of MPs reduced the accumulation of Cu in rice seedlings by 34%. We also found that, compared with only Cu present, the addition of MPs resulted in lower reactive oxygen species accumulation and higher catalase activity and glutathione levels in rice seedlings, which also contributed to Cu toxicity reduction. Collectively, the present study shows that polystyrene MPs have the potential to form associations with plant structures which can ultimately impact heavy metal bioaccessibility and therefore toxicity. Environ Toxicol Chem 2024;43:1870-1879. © 2024 SETAC.

BACKGROUND: Cadmium (Cd) pollution has declined crop yields and quality. Selenium (Se) is a beneficial mineral element that protects plants from oxidative damage, thereby improving crop tolerance to heavy metals. The molecular mechanism of Se-induced Cd tolerance in rice (Oryza sativa) is not yet understood. This study aimed to elucidate the beneficial mechanism of Se (1 mg/kg) in alleviating Cd toxicity in rice seedlings.
RESULTS: Exogenous selenium addition significantly improved the toxic effect of cadmium stress on rice seedlings, increasing plant height and fresh weight by 20.53% and 34.48%, respectively, and increasing chlorophyll and carotenoid content by 16.68% and 15.26%, respectively. Moreover, the MDA, ·OH, and protein carbonyl levels induced by cadmium stress were reduced by 47.65%, 67.57%, and 56.43%, respectively. Cell wall metabolism, energy cycling, and enzymatic and non-enzymatic antioxidant systems in rice seedlings were significantly enhanced. Transcriptome analysis showed that the expressions of key functional genes psbQ, psbO, psaG, psaD, atpG, and PetH were significantly up-regulated under low-concentration Se treatment, which enhanced the energy metabolism process of photosystem I and photosystem II in rice seedlings. At the same time, the up-regulation of LHCA, LHCB family, and C4H1, PRX, and atp6 functional genes improved the ability of photon capture and heavy metal ion binding in plants. Combined with proteome analysis, the expression of functional proteins OsGSTF1, OsGSTU11, OsG6PDH4, OsDHAB1, CP29, and CabE was significantly up-regulated under Se, which enhanced photosynthesis and anti-oxidative stress mechanism in rice seedlings. At the same time, it regulates the plant hormone signal transduction pathway. It up-regulates the expression response process of IAA, ABA, and JAZ to activate the synergistic effect between each cell rapidly and jointly maintain the homeostasis balance.
CONCLUSIONS: Our results revealed the regulation process of Se-mediated critical metabolic pathways, functional genes, and proteins in rice under cadmium stress. They provided insights into the expression rules and dynamic response process of the Se-mediated plant resistance mechanism. This study provided the theoretical basis and technical support for crop safety in cropland ecosystems and cadmium-contaminated areas.

The adversities of cadmium (Cd) contamination are quite distinguished among other heavy metals (HMs), and so is the efficacy of zinc (Zn) nutrition in mitigating Cd toxicity. Rice (Oryza sativa) crop, known for its ability to absorb HMs, inadvertently facilitates the bioaccumulation of Cd, posing a significant risk to both the plant itself and to humans consuming its edible parts, and damaging the environment as well. The use of nanoparticles, such as nano-zinc oxide (nZnO), to improve the nutritional quality of crops and combat the harmful effects of HMs, have gained substantial attention among scientists and farmers. While previous studies have explored the individual effects of nZnO or Serendipita indica (referred to as S.i) on Cd toxicity, the synergistic action of these two agents has not been thoroughly investigated. Therefore, the gift of nature, i.e., S. indica, was incorporated alongside nZnO (50 mg L-1) against Cd stress (15 μM L-1) and their alliance manifested as phenotypic level modifications in two rice genotypes (Heizhan43; Hz43 and Yinni801; Yi801). Antioxidant activities were enhanced, specifically peroxidase (61.5 and 122.5% in Yi801 and Hz43 roots, respectively), leading to a significant decrease in oxidative burst; moreover, Cd translocation was reduced (85% for Yi801 and 65.5% for Hz43 compared to Cd alone treatment). Microstructural study showed a decrease in number of vacuoles and starch granules with ameliorative treatments. Overall, plants treated with nZnO displayed gene expression pattern (particularly of ZIP genes), different from the ones with alone or combined S.i and Cd. Inferentially, the integration of nZnO and S.i holds great promise as an effective strategy for alleviating Cd toxicity in rice plants. By immobilizing Cd ions in the soil and promoting their detoxification, this novel approach contributes to environmental restoration and ensures food safety worldwide.

Low temperature severely affects rice development and yield. Ethylene signal is essential for plant development and stress response. Here, we reported that the OsEIN2-OsEIL1/2 pathway reduced OsICE1-dependent chilling tolerance in rice. The overexpressing plants of OsEIN2, OsEIL1 and OsEIL2 exhibited severe stress symptoms with excessive reactive oxygen species (ROS) accumulation under chilling, while the mutants (osein2 and oseil1) and OsEIL2-RNA interference plants (OsEIL2-Ri) showed the enhanced chilling tolerance. We validated that OsEIL1 and OsEIL2 could form a heterxodimer and synergistically repressed OsICE1 expression by binding to its promoter. The expression of OsICE1 target genes, ROS scavenging- and photosynthesis-related genes were downregulated by OsEIN2 and OsEIL1/2, which were activated by OsICE1, suggesting that OsEIN2-OsEIL1/2 pathway might mediate ROS accumulation and photosynthetic capacity under chilling by attenuating OsICE1 function. Moreover, the association analysis of the seedling chilling tolerance with the haplotype showed that the lower expression of OsEIL1 and OsEIL2 caused by natural variation might confer chilling tolerance on rice seedlings. Finally, we generated OsEIL2-edited rice with an enhanced chilling tolerance. Taken together, our findings reveal a possible mechanism integrating OsEIN2-OsEIL1/2 pathway with OsICE1-dependent cascade in regulating chilling tolerance, providing a practical strategy for breeding chilling-tolerant rice.

BACKGROUND: Rice (Oryza sativa L.) is one of the globally important staple food crops, and yield-related traits are prerequisites for improved breeding efficiency in rice. Here, we used six different genome-wide association study (GWAS) models for 198 accessions, with 553,229 single nucleotide markers (SNPs) to identify the quantitative trait nucleotides (QTNs) and candidate genes (CGs) governing rice yield.
RESULTS: Amongst the 73 different QTNs in total, 24 were co-localized with already reported QTLs or loci in previous mapping studies. We obtained fifteen significant QTNs, pathway analysis revealed 10 potential candidates within 100kb of these QTNs that are predicted to govern plant height, days to flowering, and plot yield in rice. Based on their superior allelic information in 20 elite and 6 inferior genotypes, we found a higher percentage of superior alleles in the elite genotypes in comparison to inferior genotypes. Further, we implemented expression analysis and enrichment analysis enabling the identification of 73 candidate genes and 25 homologues of Arabidopsis, 19 of which might regulate rice yield traits. Of these candidate genes, 40 CGs were found to be enriched in 60 GO terms of the studied traits for instance, positive regulator metabolic process (GO:0010929), intracellular part (GO:0031090), and nucleic acid binding (GO:0090079). Haplotype and phenotypic variation analysis confirmed that LOC_OS09G15770, LOC_OS02G36710 and LOC_OS02G17520 are key candidates associated with rice yield.
CONCLUSIONS: Overall, we foresee that the QTNs, putative candidates elucidated in the study could summarize the polygenic regulatory networks controlling rice yield and be useful for breeding high-yielding varieties.

As the source of isoprenoid precursors, the plastidial methylerythritol phosphate (MEP) pathway plays an essential role in plant development. Here, we report a novel rice (Oryza sativa L.) mutant ygl3 (yellow-green leaf3) that exhibits yellow-green leaves and lower photosynthetic efficiency compared to the wild type due to abnormal chloroplast ultrastructure and reduced chlorophyll content. Map-based cloning showed that YGL3, one of the major genes involved in the MEP pathway, encodes 4-hydroxy-3-methylbut-2-enyl diphosphate reductase, which is localized in the thylakoid membrane. A single base substitution in ygl3 plants resulted in lower 4-hydroxy-3-methylbut-2-enyl diphosphate reductase activity and lower contents of isopentenyl diphosphate (IPP) compared to the wild type. The transcript levels of genes involved in the syntheses of chlorophyll and thylakoid membrane proteins were significantly reduced in the ygl3 mutant compared to the wild type. The phytochrome interacting factor-like gene OsPIL11 regulated chlorophyll synthesis during the de-etiolation process by directly binding to the promoter of YGL3 to activate its expression. The findings provides a theoretical basis for understanding the molecular mechanisms by which the MEP pathway regulate chloroplast development in rice.

Calcium-dependent protein kinases (CPKs), the best-characterized calcium sensors in plants, regulate many aspects of plant growth and development as well as plant adaptation to biotic and abiotic stresses. However, how CPKs regulate the antioxidant defense system remains largely unknown. We previously found that impaired function of OsCPK12 leads to oxidative stress in rice, with more H2O2, lower catalase (CAT) activity, and lower yield. Here, we explored the roles of OsCPK12 in oxidative stress tolerance in rice. Our results show that OsCPK12 interacts with and phosphorylates OsCATA and OsCATC at Ser11. Knockout of either OsCATA or OsCATC leads to an oxidative stress phenotype accompanied by higher accumulation of H2O2. Overexpression of the phosphomimetic proteins OsCATAS11D and OsCATCS11D in oscpk12-cr reduced the level of H2O2 accumulation. Moreover, OsCATAS11D and OsCATCS11D showed enhanced catalase activity in vivo and in vitro. OsCPK12-overexpressing plants exhibited higher CAT activity as well as higher tolerance to oxidative stress. Our findings demonstrate that OsCPK12 affects CAT enzyme activity by phosphorylating OsCATA and OsCATC at Ser11 to regulate H2O2 homeostasis, thereby mediating oxidative stress tolerance in rice.

Rice grain quality is a multifarious attribute mainly governed by multiple nutritional factors. Grain protein is the central component of rice grain nutrition dominantly affecting eating-cooking qualities. Grain protein content is quantitatively influenced by its protein fractions. Genetic quantification of five protein fractions-albumins, globulins, prolamins, glutelin, and grain protein content-were evaluated by exploiting two BC3F2 mapping populations, derived from Kongyu131/TKM9 (population-I) and Kongyu131/Bg94-1 (population-II), which were grown in a single environment. Correlation studies among protein fractions and grain protein content were thoroughly investigated. A genetic linkage map was developed by using 146 single sequence repeat (SSR) markers in population-I and 167 markers in population-II. In total, 40 QTLs were delineated for five traits in both populations. Approximately 22 QTLs were dissected in population-I, derived from Kongyu131/TKM9, seven QTLs for albumin content, four QTLs for globulin content, three QTLs for prolamin content, four QTLs for glutelin content, and four QTLs for grain protein content. In total, 18 QTLs were detected in population-II, derived from Kongyu131/Bg94-1, five QTLs for albumin content, three QTLs for globulin content, four QTLs for prolamin content, two QTLs for glutelin content, and four QTLs for grain protein content. Three QTLs, qAlb7.1, Alb7.2, and qGPC7.2, derived from population-II (Kongyu131/Bg94-1) for albumin and grain protein content were successfully validated in the near isogenic line (NIL) populations. The localized chromosomal locus of the validated QTLs could be helpful for fine mapping via map-based cloning to discover underlying candidate genes. The functional insights of the underlying candidate gene would furnish novel perceptivity for the foundation of rice grain protein content and trigger the development of nutritionally important rice cultivars by combining marker-assisted selection (MAS) breeding.
UNASSIGNED: The online version contains supplementary material available at 10.1007/s11032-023-01436-7.

Heading date (or flowering time) is a key agronomic trait that affects seasonal and regional adaption of rice cultivars. An unoptimized heading date can either not achieve a high yield or has a high risk of encountering abiotic stresses. There is a strong demand on the mild to moderate adjusting the heading date in breeding practice. Genome editing is a promising method which allows more precise and faster changing the heading date of rice. However, direct knock out of major genes involved in regulating heading date will not always achieve a new germplasm with expected heading date. It is still challenging to quantitatively adjust the heading date of elite cultivars with best adaption for broader region. In this study, we used a CRISPR-Cas9 based genome editing strategy called high-efficiency multiplex promoter-targeting (HMP) to generate novel alleles at cis-regulatory regions of three major heading date genes: Hd1, Ghd7 and DTH8. We achieved a series of germplasm with quantitative variations of heading date by editing promoter regions and adjusting the expression levels of these genes. We performed field trials to screen for the best adapted lines for different regions. We successfully expanded an elite cultivar Ningjing8 (NJ8) to a higher latitude region by selecting a line with a mild early heading phenotype that escaped from cold stress and achieved high yield potential. Our study demonstrates that HMP is a powerful tool for quantitatively regulating rice heading date and expanding elite cultivars to broader regions.

BACKGROUND: One of the most important cash crops worldwide is rice (Oryza sativa L.). Under varying climatic conditions, however, its yield is negatively affected. In order to create rice varieties that are resilient to abiotic stress, it is essential to explore the factors that control rice growth, development, and are source of resistance. HSFs (heat shock transcription factors) control a variety of plant biological processes and responses to environmental stress. The in-silico analysis offers a platform for thorough genome-wide identification of OsHSF genes in the rice genome.
RESULTS: In this study, 25 randomly dispersed HSF genes with significant DNA binding domains (DBD) were found in the rice genome. According to a gene structural analysis, all members of the OsHSF family share Gly-66, Phe-67, Lys-69, Trp-75, Glu-76, Phe-77, Ala-78, Phe-82, Ile-93, and Arg-96. Rice HSF family genes are widely distributed in the vegetative organs, first in the roots and then in the leaf and stem; in contrast, in reproductive tissues, the embryo and lemma exhibit the highest levels of gene expression. According to chromosomal localization, tandem duplication and repetition may have aided in the development of novel genes in the rice genome. OsHSFs have a significant role in the regulation of gene expression, regulation in primary metabolism and tolerance to environmental stress, according to gene networking analyses.
CONCLUSIONS: Six genes viz; Os01g39020, Os01g53220, Os03g25080, Os01g54550, Os02g13800 and Os10g28340 were annotated as promising genes. This study provides novel insights for functional studies on the OsHSFs in rice breeding programs. With the ultimate goal of enhancing crops, the data collected in this survey will be valuable for performing genomic research to pinpoint the specific function of the HSF gene during stress responses.