Search

Key message: OsCOL5, an ortholog ofArabidopsis COL5, is involved in photoperiodic flowering and enhances rice yield through modulation ofGhd7andEhd2and interactions withOsELF3-1andOsELF3-2. Heading date, also known as flowering time, plays a crucial role in determining the adaptability and yield potential of rice (Oryza sativa L.). CONSTANS (CO)-like is one of the most critical flowering-associated gene families, members of which are evolutionarily conserved. Here, we report the molecular functional characterization of OsCOL5, an ortholog of Arabidopsis COL5, which is involved in photoperiodic flowering and influences rice yield. Structural analysis revealed that OsCOL5 is a typical member of CO-like family, containing two B-box domains and one CCT domain. Rice plants overexpressing OsCOL5 showed delayed heading and increases in plant height, main spike number, total grain number per plant, and yield per plant under both long-day (LD) and short-day (SD) conditions. Gene expression analysis indicated that OsCOL5 was primarily expressed in the leaves and stems with a diurnal rhythm expression pattern. RT-qPCR analysis of heading date genes showed that OsCOL5 suppressed flowering by up-regulating Ghd7 and down-regulating Ehd2, consequently reducing the expression of Ehd1, Hd3a, RFT1, OsMADS14, and OsMADS15. Yeast two-hybrid experiments showed direct interactions of OsCOL5 with OsELF3-1 and OsELF3-2. Further verification showed specific interactions between the zinc finger/B-box domain of OsCOL5 and the middle region of OsELF3-1 and OsELF3-2. Yeast one-hybrid assays revealed that OsCOL5 may bind to the CCACA motif. The results suggest that OsCOL5 functions as a floral repressor, playing a vital role in rice’s photoperiodic flowering regulation. This gene shows potential in breeding programs aimed at improving rice yield by influencing the timing of flowering, which directly impacts crop productivity. [ABSTRACT FROM AUTHOR]

• The antibiotics were not detected in grains and heavy metals did not exceed limits. • MRGs ruvB and acn , and ARGs sul1 and sul2 were the dominating resistant genes. • Co-selection may serve as a potential mechanism for resistance maintenance. • MRG CzcA and ARG sul1 can be recommended as model genes to study the co-selection. • Proteobacteria were the most influential hosts for MRG, ARG, and integrons. Secondary municipal-treated wastewater irrigation may introduce residual antibiotics into the agricultural systems contaminated with certain heavy metals, ultimately leading to the coexistence of antibiotics and heavy metals. The coexistence may induce synergistic resistance to both in the microbial community. Here, we investigated the effects of long-term municipal-treated irrigation for rice on the microbiome and resistome. The results showed that the target antibiotics were undetectable in edible grains, and the heavy metal concentrations did not exceed the standard in edible rice grains. Heavy metal resistance genes (MRGs) ruvB and acn antibiotic resistance genes (ARGs) sul1 and sul2 were the dominating resistant genes. The coexistence of antibiotics and heavy metals affected the microbial community and promoted metal and antibiotic resistance. Network analysis revealed that Proteobacteria were the most influential hosts for MRGs, ARGs, and integrons, and co-selection may serve as a potential mechanism for resistance maintenance. MRG czcA and ARG sul1 can be recommended as model genes to study the co-selection of ARGs and MRGs in environments. The obtained results highlight the importance of considering the co-occurrence of heavy metals and antibiotics while developing effective methods to prevent the transmission of ARGs. These findings are critical for assessing the possible human health concerns associated with secondary municipal-treated wastewater irrigation for agriculture and improving the understanding of the coexistence of heavy metals and antibiotics. [Display omitted] [ABSTRACT FROM AUTHOR]

Flowering time or heading date in rice is an important agronomic trait that determines cultivation area and cropping season of a given variety. The genes/loci that have minor effect on the heading date are believed to play a critical role in adaptation of rice to different geographical regions and are preferred by breeders. Previously, we detected a stable minor-effect quantitative trait locus, qDTH-3b (for Days to heading3b; hereafter referred to as DTH3b), using a small population consisting of recombinant inbred lines derived from a cross between the japonica cv. Asominori (Aso) and the indica cv. IR24. However, its precise location remains to be defined. In this study, we fine-mapped DTH3b by using advanced backcrossing lines and explored its role in regulating the heading date. First, we constructed a BC4F2 population by backcrossing a chromosome segment substitution line (CSSL23) with Aso as a recurrent parent. Then, we developed a near-isogenic line (NIL) from this population by marker-assisted selection. This NIL has the genetic background of Aso but carries a 12-cM DTH3b-containing chromosome segment from IR24. Compared with Aso, the NIL showed 6.9-day delay in flowering time and 63.8 % lower seed maturation rate under long-day (LD) conditions, whereas there was no significant difference between the NIL and Aso under short-day conditions. Using a total of 1500 Asominori/NIL F2:3 or F3:4 late-heading families grown under LD conditions, we finally dissected DTH3b to a single Mendelian factor and delimited it to a 46-kb genomic region which contains seven open reading frames. Further, our quantitative real-time PCR analysis indicated that transcription level of Hd3a (Heading date 3a) and RFT1 (RICE FLOWERING LOCUS T 1), the two florigen genes, was significantly lower in the NIL than in Aso, suggesting that DTH3b functions upstream of Hd3a and RFT1 under LD conditions. We propose that DTH3bAso positively regulates flowering time and contributes to adaptation of rice to the north. Cloning and then manipulation of DTH3b can be a useful approach to optimize flowering time in rice breeding. [ABSTRACT FROM AUTHOR]

Heading date is a key determinant of regional and seasonal adaptation in rice ( Oryza sativa L.). A minor-effect quantitative trait locus (QTL), QTL for D ays t o h eading 12a ( qDTH- 12a), with unknown genetic action was previously coarsely detected in a recombinant inbred line population. The study reported here was designed to better define the qDTH- 12a locus (designated as DTH12) in advanced segregating populations. DTH12 was initially verified in chromosome segment substitution line CSSL84. A CSSL84/Asominori//Asominori BCF population was then developed, and a near-isogenic line (NIL), NIL( DTH12), was subsequently selected from this population using marker-assisted tracking that headed 8 days later than Asominori under long-day (LD) conditions but which was not significantly different in heading date in short-day environments. Using 358 Asominori/NIL( DTH12) F families grown under LD conditions, we were able to initially map DTH12 to a 26-cM interval between markers InDel12-1 and RM6296. F individuals heterozygous for the DTH12 regions were then chosen, and 2,388 F families were used for fine mapping. DTH12 was finally dissected as a single gene and delimited to a 153-kb genomic region with 32 open reading frames. Compared with Asominori, NIL( DTH12) showed reduced transcription of the florigen genes Heading date 3a and RICE FLOWERING LOCUS T 1, suggesting that DTH12 functions as an up-regulator of florigen genes during floral induction under LD conditions. DTH12 was also found to have an important role in rice adaptation and breeding for precise control of seed maturity. These findings provide a firm basis for cloning this minor-effect QTL involved in rice flowering. [ABSTRACT FROM AUTHOR]

Sheath blight disease (ShB) is considered to be the second most important disease affecting rice, and the genetic mechanism of ShB resistance in rice is great complicated. Uncovering genetic mechanism of ShB resistance and strong resistant varieties in rice are the premise for ShB resistance improvement. A rice ShB genome-wide association study (GWAS) was performed using approximately five million SNPs within Ting's core collection. "Early pradifice", one typical japonica, was determined to be the most resistant variety in both 2016 and 2017. A total of 34 and four significant (p ≤ 1.93 × 10−8) SNPs were observed in 2016 and 2017, respectively. Moreover, 23 of 34 and two of four gene-based SNPs not reported in previous studies in 2016 and 2017, respectively, were identified as significantly associated with rice ShB resistance. Furthermore, we performed GO (gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses for the genes located at a region within 10 kb of the significant SNPs. Both in 2016 and 2017, we observed that genes were uniquely enriched in the regulation of transcription and RNA processing in the category of "biological process", plasma membrane, nucleus, integral component of membrane and cell wall in the category of "cellular component", and ATP binding in the category of "molecular function". The results of the present study may establish a foundation for further research investigating these elite genes and utilizing the resistant varieties in Ting's core collection to improve rice ShB resistance. [ABSTRACT FROM AUTHOR]

Background: The genetic mechanism of aluminum (Al) tolerance in rice is great complicated. Uncovering genetic mechanism of Al tolerance in rice is the premise for Al tolerance improvement. Mining elite genes within rice landrace is of importance for improvement of Al tolerance in rice. Results: Genome-wide association study (GWAS) performed in EMMAX for rice Al tolerance was carried out using 150 varieties of Ting's core collection constructed from 2262 Ting's collections with more than 3.8 million SNPs. Within Ting's core collection of clear population structure and kinship relatedness as well as high rate of linkage disequilibrium (LD) decay, 17 genes relating to rice Al tolerance including cloned genes like NRAT1, ART1 and STAR1 were identified in this study. Moreover, 13 new candidate regions with high LD and 69 new candidate genes were detected. Furthermore, 20 of 69 new candidate genes were detected with significant difference between Al treatment and without Al toxicity by transcriptome sequencing. Interestingly, both qRT-PCR and sequence analysis in CDS region demonstrated that the candidate genes in present study might play important roles in rice Al tolerance. Conclusions: The present study provided important information for further using these elite genes existing in Ting's core collection for improvement of rice Al tolerance. [ABSTRACT FROM AUTHOR]

Improving rice aluminum (Al) tolerance in acid soils is highly significant to rice production. So far, no molecular marker which can efficiently identify rice Al tolerance has been developed. In this study, Art1, a primer specific for the ART1 gene was designed to study whether some natural variations exist in ART1 between Al tolerant and sensitive varieties. The results showed that two Al tolerant varieties had identical nucleotides and amino acids, while three Al sensitive varieties had the same nucleotides and amino acids differing from the two Al tolerant varieties. The same results were discovered within 150 rice varieties of Ting's core collection. Art1 could be used to judge rice Al tolerance. [ABSTRACT FROM AUTHOR]

Background: Cultivated rice (Oryza sativa L.) is one of the staple food for over half of the world's population. Thus, improvement of cultivated rice is important for the development of the world. It has been shown that abundant elite genes exist in rice landraces in previous studies. Results: A genome-wide association study (GWAS) performed with EMMAX for 12 agronomic traits measured in both Guangzhou and Hangzhou was carried out using 150 accessions of Ting's core collection selected based on 48 phenotypic traits from 2262 accessions of Ting's collection, the GWAS included more than 3.8 million SNPs. Within Ting's core collection, which has a simple population structure, low relatedness, and rapid linkage disequilibrium (LD) decay, we found 32 peaks located closely to previously cloned genes such as Hd1, SD1, Ghd7, GW8, and GL7 or mapped QTL, and these loci might be natural variations in the cloned genes or QTL which influence potentially agronomic traits. Furthermore, we also detected 32 regions where new genes might be located, and some peaks of these new candidate genes such as the signal on chromosome 11 for heading days were even higher than that of Hd1. Detailed annotation of these significant loci were shown in this study. Moreover, according to the estimated LD decay distance of 100 to 350 kb on the 12 chromosomes in this study, we found 13 identical significant regions in the two locations. Conclusions: This research provided important information for further mining these elite genes within Ting's core collection and using them for rice breeding. [ABSTRACT FROM AUTHOR]

Aluminum (Al) at high concentrations inhibits root growth, damage root systems, and causes significant reductions in rice yields. Indica and Japonica rice have been cultivated in distinctly different ecological environments with different soil acidity levels; thus, they might have different mechanisms of Al-tolerance. In the present study, transcriptomic analysis in the root apex for Al-tolerance in the seedling stage was carried out within Al-tolerant and -sensitive varieties belonging to different subpopulations (i.e., Indica, Japonica, and mixed). We found that there were significant differences between the gene expression patterns of Indica Al-tolerant and Japonica Al-tolerant varieties, while the gene expression patterns of the Al-tolerant varieties in the mixed subgroup, which was inclined to Japonica, were similar to the Al-tolerant varieties in Japonica. Moreover, after further GO (gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analyses of the transcriptomic data, we found that eight pathways, i.e., "Terpenoid backbone biosynthesis", "Ribosome", "Amino sugar and nucleotide sugar metabolism", "Plant hormone signal transduction", "TCA cycle", "Synthesis and degradation of ketone bodies", and "Butanoate metabolism" were found uniquely for Indica Al-tolerant varieties, while only one pathway (i.e., "Sulfur metabolism") was found uniquely for Japonica Al-tolerant varieties. For Al-sensitive varieties, one identical pathway was found, both in Indica and Japonica. Three pathways were found uniquely in "Starch and sucrose metabolism", "Metabolic pathway", and "Amino sugar and nucleotide sugar metabolism". [ABSTRACT FROM AUTHOR]

Asian cultivated rice ( Oryza sativa L.) and African cultivated rice ( Oryza glaberrima Steud.) are the two main cultivated rice species in the world, with strong heterosis in their F1 hybrids. However, hybrid sterility is a major barrier, although significant heterosis has been observed. In this study, an F1 pollen semi-sterility locus, S19, was identified on rice chromosome 3 by using near-isogenic lines derived from repeated backcross and marker-assisted selection. The typical pollen semi-sterility was observed in F1 hybrids between S19-NIL and Dianjingyou 1. Cytological study of pollen developmental stages indicated that pollen abortion occurred at the late binucleate stage because of a starch accumulation obstacle in some pollen grains. Molecular analysis revealed that the semi-sterility was caused by the abortion of most male gametophytes carrying the S19 allele from the japonica variety Dianjingyou 1. In a population of 12,780 F2 plants derived from S19-NIL/Dianjingyou 1, the S19 locus was fine-mapped to a chromosomal region of 54 kb based on BAC clones of cv. Nipponbare. Interestingly, an addition of a DNA fragment of about 89 kb to the 54-kb region was found in S19-NIL based on BAC clones of O. glaberrima. Gene prediction analysis identified 12 open reading frames (ORF) based on the region of Dianjingyou 1, while 32 ORFs were predicted in S19-NIL. Map-based cloning of this gene will help us to understand the underlying mechanism of hybrid sterility between the two cultivated rice species. [ABSTRACT FROM AUTHOR]