Grain length (size) and weight are essential components of crop yield. To date, many QTLs/genes for these traits have been identified. GS3 encodes a putative transmembrane protein and functions as a negative regulator, and its larger-grain allele contains a nonsense mutation causing a 178-aa truncation (Fan et al., 2006). GL3.1/qGL3 encodes a putative protein phosphatase and also acts as a negative regulator of grain size (Qi et al., 2012;Zhang et al., 2012). Another negative regulator of grain size and weight is TGW6, which hydrolyzes indole-3-acetic acid (IAA)-glucose into IAA and glucose (Ishimaru et al., 2013). In contrast, GW6a is a positive regulator of grain weight, which encodes a novel histone H4 acetyltransferase (Song et al., 2015). Copy number variation at the GL7/GW7 locus causes elevated expression of GL7 and thus an increase in grain length (Wang et al., 2015a(Wang et al., , 2015b. GL2/GS2 encodes the plant-specific transcription factor OsGRF4, and its larger-grain allele harbors a mutation preventing cleavage by miR396c, resulting in elevated GL2/GS2 expression (Hu et al., 2015;Che et al., 2016). GLW7 encodes the plantspecific transcription factor OsSPL13, and high OsSPL13 expression is associated with larger grains (Si et al., 2016). These findings have greatly enhanced our understanding of grain length and weight regulation; however, there are still gaps in integrating these factors into genetic network(s). Here, we report a thorough dissection of the QTL composition of grain size and the characterization of a novel QTL, qTGW3, that regulates grain length and weight in rice.
China's soils tend to be phosphate deficient. Application of phosphorus fertilisers to the soil is yield and cost ineffective as much of the phosphate applied is rapidly locked-in and is inaccessible to the crop. Chinese Institutes have established intensive wheat breeding programmes to generate wheat varieties that produce adequate yields and grain quality in such soils. Three such wheat cultivars have been identified with good performance characteristics in the field. These three cultivars are thought to harbour chromosome translocations that may confer enhanced phosphate scavenging abilities to the plants. The isolation and study of the expression of high-affinity phosphate transporters in tissues of these wheats, in two of the donor wheatgrasses and in another widely planted Chinese wheat variety is presented and the first full-length sequence of a wheat phosphate transporter and partial clones of several other putative phosphate transporters are reported. Relative quantitative reverse-transcription -polymerase chain-reaction was used to demonstrate that different phosphate transporters have different expression patterns within a given variety and respond differently to phosphate deprivation. The significance of the genetic background for these findings and for the different phosphate acquisition properties of the wheats under study is discussed.
Plant seed oil is important for human dietary consumption and industrial application. The oil trait is controlled by quantitative trait loci (QTLs), but no QTLs for fatty acid composition are known in rice, the monocot model plant. QTL analysis was performed using F(2) and F(2:3) progeny from a cross of an indica variety and a japonica variety. Gas chromatography-mass spectrometry (GC-MS) analysis revealed significant differences between parental lines in fatty acid composition of brown rice oil, and 29 associated QTLs in F(2) and/or F(2:3) populations were identified throughout the rice genome, except chromosomes 9 and 10. Eight QTLs were repeatedly identified in both populations across different environments. Five loci pleiotropically controlled different traits, contributing to complex interactions of oil with fatty acids and between fatty acids. Nine rice orthologs of Arabidopsis genes encoding key enzymes in lipid metabolism co-localized with 11 mapped QTLs. A strong QTL for oleic (18:1) and linoleic (18:2) acid were associated with a rice ortholog of a gene encoding acyl-CoA:diacylglycerol acyltransferase (DGAT), and another for palmitic acid (16:0) mapped similarly to the acyl-ACP thioesterase (FatB) gene ortholog. Our approach rapidly and efficiently identified candidate genes for mapped QTLs controlling fatty acid composition and oil concentration, providing information for improving rice grain quality by marker assisted selection.
Key messageA minor QTL for heading date located on the long arm of rice chromosome 1 was delimitated to a 95.0-kb region using near isogenic lines with sequential segregating regions.AbstractHeading date and grain yield are two key factors determining the commercial potential of a rice variety. In this study, rice populations with sequential segregating regions were developed and used for mapping a minor QTL for heading date, qHd1. A total of 18 populations in six advanced generations through BC2F6 to BC2F11 were derived from a single BC2F3 plant of the indica rice cross Zhenshan 97 (ZS97)///ZS97//ZS97/Milyang 46. The QTL was delimitated to a 95.0-kb region flanked by RM12102 and RM12108 in the terminal region of the long arm of chromosome 1. Results also showed that qHd1 was not involved in the photoperiodic response, having an additive effect ranging from 2.4 d to 2.9 d observed in near isogenic lines grown in the paddy field and under the controlled conditions of either short day or long day. The QTL had pleiotropic effects on yield traits, with the ZS97 allele delaying heading and increasing the number of spikelets per panicle, the number of grains per panicle and grain yield per plant. The candidate region contains ten annotated genes including two genes with functional information related to the control of heading date. These results lay a foundation for the cloning of qHd1. In addition, this kind of minor QTLs could be of great significance in rice breeding for allowing minor adjustment of heading date and yield traits.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-014-2395-7) contains supplementary material, which is available to authorized users.
BackgroundRice is highly sensitive to temperature fluctuations. Recently, the frequent occurrence of high temperature stress has heavily influenced rice production. Proper heading date in specific environmental conditions could ensure high grain yield. Rice heading greatly depends on the accurate measurement of environmental changes, particularly in day length and temperature. In contrary to the detailed understanding of the photoperiod pathway, little has been known about how temperature regulates the genetic control of rice heading.ResultsNear isogenic lines that were segregated for qHd1, were developed from a cross between indica rice varieties Zhenshan 97 (ZS97) and Milyang 46 (MY46). Using a five sowing-date experiment in the paddy field, we observed the involvement of qHd1 in temperature responses. With the gradual increase of temperature from Trial I to V, heading date of MY46 homozygotes continued to decrease for about 5 d per trial from 76 to 58 d, while that of ZS97 homozygotes was promoted at the same rate from Trial I to III and then stabilized at 69 d. This thermal response was confirmed in a temperature-gradient experiment conducted in the phytotron. It is also found that tolerance of the ZS97 allele to heading acceleration at high temperature was associated with higher grain weight that resulted in higher grain yield. Then, by qRT-PCR and RNA-seq, we found the pathway OsMADS51-Ehd1-RFT1/Hd3a underlying the qHd1-mediated floral response to temperature. By sequence comparison, OsMADS51 for qHd1 displayed a 9.5-kb insertion in the 1st intron of the ZS97 allele compared to the MY46 allele. Furthermore, this large insertion is commonly found in major early-season indica rice varieties, but not in the middle- and late-season ones, which corresponds to the requirement for high-temperature tolerance during the heading and grain-filling stages of early-season rice.ConclusionsBeneficial alleles at qHd1 confer tolerance to high temperatures at the heading and grain-filling stages, playing a significant role in the eco-geographical adaptation of early-season indica rice during modern breeding. These results, together with the underlying OsMADS51-Ehd1-RFT1/Hd3a floral pathway, provide valuable information for better understanding the molecular mechanism of temperature responsive regulation of heading date and yield traits in rice.Electronic supplementary materialThe online version of this article (10.1186/s12870-018-1330-5) contains supplementary material, which is available to authorized users.
Important role of flowering genes in enhancing grain productivity in rice has become well recognized for a number of key genes regulating the florigen production, but little has been known for the two florigen genes themselves. In this study, pleiotropism of Rice Flowering Locus T 1 (RFT1), one of the two florigen genes in rice, was firstly evaluated using near isogenic lines (NILs) carrying RFT1 alleles from the indica rice cultivars Zhenshan 97 (ZS97) and Milyang 46, respectively, and then determined by transformation of the RFT1 ZS97 allele into a japonica rice variety, Zhonghua 11. The RFT1 ZS97 allele was shown to delay heading and increase plant height, grain weight, grain number and grain yield, indicating that RFT1 plays an important role in the growth and development of rice. This study has also validated the potential of using a new type of genetic resource, sequential residual heterozygotes (SeqRHs), for QTL fine-mapping. A step-by-step approach was employed for SeqRHs identification, NIL development and QTL fine-mapping. The heterozygous segments and candidate QTL regions were gradually narrowed down. Eventually, the QTL region was delimited to a 1.7 kb region containing a single gene.
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