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Comparison of endosperm development in weedy rice (Oryza sativa f. spontanea) and cultivated rice (Oryza sativa). Microstructure of endosperm cell of the weedy rice and associated cultivated rice (ACR). The transverse sections of endosperm at 3, 5, 7, and 9 d post-anthesis (DPA) were used for the observation of microstructure. N, nucleus; ES, endosperm; A, amyloplast; Cv, central vacuole; Nu, nucellus; NE, nucellar epidermis; FN, free nucleus; NP, nucellar projection; DV, dorsal vascular bundle; AL, aleurone layer; Pe, pericarp; Enc, endocarp. Ecw, endosperm cell wall; NP, nucellar projection; PB, pigment bundle; II, inner integument.
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Early maturity allows weedy rice ( Oryza sativa L. f. spontanea ) to persist by escaping harvest in paddy fields. A shorter grain-filling period contributes to the early maturity of weedy rice. However, the differences in morphology and endosperm development in the caryopsis between weedy and cultivated rice are largely unexplored. Here, we selecte...
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... change in color of weedy rice was 2 to 5 d earlier than that in cultivated rice ( The endosperm cells of weedy rice completed the cellularization stage at 3 DPA and had more amyloplasts. Compared with that of ACR, the starch accumulation of weedy rice was faster, and the starch grains in the endosperm were arranged more closely (Figure 3). The outer layers of endosperm cells transformed into aleurone layer cells 7 d after flowering in the small-grain cultivated varieties but 10 d after flowering in the large-grain cultivated varieties ( Chen et al. 2009). ...
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... has been reported that at 1 to 2 d after anthesis, the endosperm of rice was in the coenocyte stage ( Wei et al. 2002;Yu et al. 2014), which is consistent with our results. We showed that the endosperm cells of weedy and cultivated rice were in the coenocyte stage at 1 to 2 d after anthesis (Figure 3). At 3 DPA, the endosperm cells of weedy rice cellularized earlier and more rapidly than those of ACR. ...
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... formed 6 layers of endosperm cells at 3 DPA, while TZCR remained at the coenocytic stage at 3 DPA. From 5 DPA to 9 DPA, both TZWR and TZCR rapidly accumulated starch, but the starch grains in weedy rice were arranged more closely than those in cultivated rice (Figure 3). YZWR had finished the cellularization stage at 3 DPA, and a small amount of starch grains had accumulated in the endosperm cells, while YZCR had formed only 6 to 7 layers of endosperm cells at 3 DPA without stored starch grains. ...
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... YZWR and YZCR differentiated the aleurone layer from 5 DPA to 9 DPA, and there was a large amount of starch accumulation in the endosperm. Compared with those of YZCR, the amyloplasts of YZWR were larger, and the starch grains were arranged more closely (Figure 3). MMWR had finished the cellularization stage at 3 DPA, and its outer layer cells of endosperm had already stored some small amyloplasts, while MMCR had formed only 3 to 4 layers of endosperm cells at 3 DPA without stored starch grains (Figure 3). ...
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... with those of YZCR, the amyloplasts of YZWR were larger, and the starch grains were arranged more closely (Figure 3). MMWR had finished the cellularization stage at 3 DPA, and its outer layer cells of endosperm had already stored some small amyloplasts, while MMCR had formed only 3 to 4 layers of endosperm cells at 3 DPA without stored starch grains (Figure 3). DDWR had already finished cellularization at 3 DPA, and the endosperm cells were fully formed in the endosperm with some small amyloplasts stored, while DDCR had formed only 2 layers of endosperm cells at 3 DPA (Figure 3). ...
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... had finished the cellularization stage at 3 DPA, and its outer layer cells of endosperm had already stored some small amyloplasts, while MMCR had formed only 3 to 4 layers of endosperm cells at 3 DPA without stored starch grains (Figure 3). DDWR had already finished cellularization at 3 DPA, and the endosperm cells were fully formed in the endosperm with some small amyloplasts stored, while DDCR had formed only 2 layers of endosperm cells at 3 DPA (Figure 3). Li et al. (2014) found that compared with the late-maturing cultivar, the early-maturing cultivar had faster grain development, which was consistent with our observations. ...
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... cell proliferation mainly occurs at the cellularization stage ( Wei et al. 2002;Yu et al. 2014). We determined that weedy rice had finished cellularization at 3 DPA and already stored some small starch grains in endosperm cells (Figures 3 and 4). However, the cultivated rice was still at the cellularization stage, had formed fewer cell layers, and had no starch grain stored in the endosperm at 3 DPA. ...
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Citations
... The early maturation and shattering ability of weedy rice are well-recognized traits that can help its seeds to escape harvest, enter the soil seed bank, and hence persist in paddy fields over subsequent growing seasons (Gu et al., 2003;Thurber et al., 2010;Zhao et al., 2019). A less-well studied but potentially equally important trait is stem lodging, whereby the stems of the maturing plant fail to maintain erect growth and bend over at the stem base. ...
... Weedy rice has many morphological and physiological characteristics related to weediness, such as high phenotypic plasticity, rapid germination and growth, early seed maturity, easy seed shattering, long seed dormancy, and long lifespan (Delouche et al., 2007;Thurber et al., 2010;Andres et al., 2015;Dai et al., 2017;Zhao et al., 2019). The lodging ability of weedy rice is also a weediness trait that could synergize with early maturity, seed shattering, and dormancy to increase its continuity over successive growing seasons, which is an important survival strategy for it to persist in paddy fields. ...
Weedy rice (Oryza spp.), one of the most notorious weeds in rice fields, evades eradication through stem lodging and seed shattering. Many studies have focused on seed shattering in weedy rice. However, the lodging differentiation of weedy rice in different regions of China has not been characterized, and the underlying mechanisms of lodging difference between weedy rice and associated cultivated rice have not been studied in detail. Here, we compared the lodging variation among diverse Chinese weedy rice strains and between weedy rice and co-occurring cultivated rice. The chemical composition of basal stems was determined, and transcriptome and methylome sequencing were used to assess the expression variation of lodging-related genes. Results showed that the lodging degree varies between indica-derived weed strains with high lodging levels, which occurred predominantly in southern China, and japonica-derived strains with lower lodging levels found primarily in the north. The more lodging-prone indica weedy rice had a smaller bending stress and lower lignin content than non-lodging accessions. In comparison to co-occurring cultivated rice, the ratio of cellulose to lignin content in lodging-prone weedy rice was lower. DNA methylation variation of lignin synthesis-related OsSWN1, OsMYBX9, OsPAL1 and Os4CL3 mediated their expression level differnece and affected the ratio of cellulose to lignin content. Together, DNA methylation in lignin-related genes regulates stem strength and lodging variations in weedy rice, and between weed strains and their co-occurring cultivated rice.
... Actin was used as the control. and black) or the elimination of color (white; Zhao et al., 2020). Chlorophyll is a highly photosensitive photosynthetic pigment, and temperature is also a critical abiotic factor influencing Chl accumulation (Ding et al., 2020). ...
The weedy rice ( Oryza sativa f. spontanea ) pericarp has diverse colors (e.g., purple, red, light-red, and white). However, research on pericarp colors has focused on red and purple, but not green. Unlike many other common weedy rice resources, LM8 has a green pericarp at maturity. In this study, the coloration of the LM8 pericarp was evaluated at the cellular and genetic levels. First, an examination of their ultrastructure indicated that LM8 chloroplasts were normal regarding plastid development and they contained many plastoglobules from the early immature stage to maturity. Analyses of transcriptome profiles and differentially expressed genes revealed that most chlorophyll (Chl) degradation-related genes in LM8 were expressed at lower levels than Chl a / b cycle-related genes in mature pericarps, suggesting that the green LM8 pericarp was associated with inhibited Chl degradation in intact chloroplasts. Second, the F 2 generation derived from a cross between LM8 (green pericarp) and SLG (white pericarp) had a pericarp color segregation ratio of 9:3:4 (green:brown:white). The bulked segregant analysis of the F 2 populations resulted in the identification of 12 known genes in the chromosome 3 and 4 hotspot regions as candidate genes related to Chl metabolism in the rice pericarp. The RNA-seq and sqRT-PCR assays indicated that the expression of the Chl a / b cycle-related structural gene DVR (encoding divinyl reductase) was sharply up-regulated. Moreover, genes encoding magnesium-chelatase subunit D and the light-harvesting Chl a / b -binding protein were transcriptionally active in the fully ripened dry pericarp. Regarding the ethylene signal transduction pathway, the CTR (encoding an ethylene-responsive protein kinase) and ERF (encoding an ethylene-responsive factor) genes expression profiles were determined. The findings of this study highlight the regulatory roles of Chl biosynthesis- and degradation-related genes influencing Chl accumulation during the maturation of the LM8 pericarp.
... Weedy rice (Oryza sativa L. f. spontanea, WR) has become one of the most harmful weeds in paddy fields worldwide (Azmi and Karim, 2008;Burgos et al., 2014;Kraehmer et al., 2016;Zhao et al., 2018Zhao et al., , 2020. It belongs to the same genus as cultivated rice (O. ...
... Both WR and CR share similar morphological and physiological traits, which make controlling WR very difficult compared to other weeds (Chauhan, 2013). WR has many morphological and physiological characteristics related to weediness, such as a rapid growth rate, high phenotypic plasticity, early maturity, seed shattering, long seed dormancy, and longevity, which facilitate seed dispersal and persistence in paddy fields (Azmi and Karim, 2008;Burgos et al., 2014;Dai et al., 2014Dai et al., , 2017Zhao et al., 2018Zhao et al., , 2020. These characteristics contribute to its competitive advantage over CR in rice production areas globally (Delouche et al., 2007). ...
... Our previous study found that the shorter grain-filling period promotes early maturity in WR compared with the associated cultivated rice (ACR) (Zhao et al., 2018). Furthermore, the rapid development of endosperm cells and starch grains leads to the shorter grainfilling period of WR (Zhao et al., 2020). The endosperm accounts for 91-92% of the total weight of rice grains. ...
Shorter grain-filling period and rapid endosperm development endow weedy rice (WR) with early maturity compared to cultivated rice (CR). However, the role of the cytological features and antioxidative enzyme system during grain development are largely unexplored. We selected four biotypes of WR and their associated cultivated rice (ACR) types from different latitudes to conduct a common garden experiment. The difference in the cytological features of endosperm between WR and ACR was compared by chemical staining, and the cell viability and nuclear morphometry of endosperm cells were observed by optical microscopy. Furthermore, antioxidative enzyme activity was measured during grain filling. Anatomic observation of endosperm shows that the development process of endosperm cell in WR was more rapid and earlier than that in ACR. The percentage of degraded nuclei of WR was 2–83% more than that of ACR. Endosperm cells in WR lost viability 2–6 days earlier than those in ACR. The antioxidant enzyme activity of WR was lower than that of ACR during grain filling. The ability of WR to scavenge reactive oxygen species (ROS) was weaker than that of ACR, which may contribute to the rapid cytological process in the endosperm cells of WR. The rapid cytological process and weaker ability to scavenge ROS in endosperm cells may contribute to early maturity in WR.
... In addition, weedy rice has heavy shattering, which contribute to weedy rice escape from harvesting (Zhao et al. 2018). Furthermore, the rapid development of endosperm cells and starch grains leads to the shorter grain-lling period of weedy rice (Zhao et al. 2020). However, the relationship between the process of programmed cell death (PCD) in endosperm cells and the early maturity of weedy rice was unclear. ...
... There are many reports about the PCD process of cultivated rice, but the research of PCD process contribute to early maturity in weedy rice has not been reported. In previous research, we found that shorter grain-lling stages contribute to the early maturity of weedy rice, and the rapid development of endosperm cells and starch grains leads to the shorter grain-lling period of weedy rice (Zhao et al. 2018(Zhao et al. , 2020. In the present study, we used Steedman's wax embedded sections, DAPI staining, Evans blue staining and TTC staining to compare and analyze the difference of PCD process in endosperm cells between weedy rice and cultivated rice, and compare the difference of antioxidative enzymes system enzyme activity between weedy rice and cultivated rice during grain lling. ...
Background: Shorter grain-filling period and rapid endosperm development contributes to early maturity in weedy rice (Oryza sativa L. f. spontanea). However, the differences in programmed cell death (PCD) process and anti-oxidative enzymes system in the caryopsis between weedy and cultivated rice are largely unexplored.
Main Text: we selected four biotypes of weedy rice and associated cultivated rice (ACR, Oryza sativa) from different latitudes to conduct a common garden experiment. The difference of PCD process between weedy rice and ACR was compared by chemical staining, and the cell viability and nuclear morphometry of endosperm cells were observed by optical microscopy, and anti-oxidative enzymes activity were also measured during grain filling. We found that the PCD progress in weedy rice was more rapid and earlier than that in ACR. The percentage of degraded nuclei of weedy rice were 10%-83% higher than that of ACR. Endosperm cells in weedy rice lost cell viability 2-8 days earlier than that in ACR. The anti-oxidant enzymes activity of weedy rice were lower than that of ACR during grain filling. The ability of weedy rice to scavenge reactive oxygen species is weaker than that of ACR, which may contribute to the rapid PCD process in the endosperm cells of weedy rice.
Conclusion: The rapid PCD process and weaker ability to scavenge reactive oxygen species in endosperm cells lead to the shorter grain-filling period of weedy rice.
Oat (Avena sativa) is a cereal crop whose grains are rich in (1,3; 1,4)-β-D-glucan (mixed linkage glucan or MLG), a soluble dietary fiber. In our study, we analyzed oat endosperm development in two Canadian varieties with differing MLG content and nutritional value. We confirmed that oat undergoes a nuclear type of endosperm development but with a shorter cellularisation phase than barley (Hordeum vulgare). Callose and cellulose were the first polysaccharides to be detected in the early anticlinal cell walls at 11 days post-emergence (DPE) of the panicle. Other polysaccharides such as heteromannan and homogalacturonan were deposited early in cellularisation around 12 DPE after the first periclinal walls are laid down. In contrast to barley, heteroxylan deposition coincided with completion of cellularisation and was detected from 14 DPE but was only detectable after demasking. Notably, MLG was the last polysaccharide to be laid down at 18 DPE within the differentiation phase, rather than during cellularisation. In addition, differences in the spatiotemporal patterning of MLG were also observed between the two varieties. The lower MLG-containing cultivar AC Morgan (3.5% w/w groats) was marked by the presence of a discontinuous pattern of MLG labelling, while labelling in the same walls in CDC Morrison (5.6% w/w groats) was mostly even and continuous. RNA-Seq analysis revealed higher transcript levels of multiple MLG biosynthetic Cellulose Synthase-like F (CSLF) and CSLH) genes during grain development in CDC Morrison compared to AC Morgan that likely contributes to the increased abundance of MLG at maturity in CDC Morrison. CDC Morrison was also observed to have smaller endosperm cells with thicker walls than AC Morgan from cellularisation onwards, suggesting the processes controlling cell size and shape are established early in development. This study has highlighted that the molecular processes influencing MLG content and deposition are more complex than previously imagined.
Rice, the main food crop in China, has been sporadically reported to suffer from weedy rice infestation. However, the overall occurrence and distribution pattern of weedy rice in China remains unclear because a systematic survey has not been conducted. In order to reveal the infestation of weedy rice in China, a field survey was conducted in 999 sampling sites all over the rice-growing regions in China from 2009 to 2016 using seven-scale visual scoring of the level of weed infestation. Weedy rice was found 39% occurrence incidence in a total of 387 sites. The sampling sites with 50% or higher Overall Weedy rice Infestation Index mainly radiated from Jiangsu, Heilongjiang, Ningxia and Guangdong to East China, Northeast China, Northwest China and South China. A total of 45 morphological characters from 287 populations (collected simultaneously with the field survey) out of those occurred sites were observed and analyzed using multivariate analysis in common gardens with the same cultivation conditions in 2017 and 2019. Canonical correlation analysis showed that 45 morphological characters were significantly related to latitude, mean temperature, minimum temperature, precipitation and mean diurnal range factors. The 287 weedy rice populations were divided into three morphological groups with climate-dependent geographical differentiation: strong tiller type only in Jiangsu, large leaf type in southern and central regions and large grain type mainly in north China. Weedy rice seriously infested rice fields and had a geography, climate and cultivated rice type-dependent morphological and biotype differentiation in China. It is suggested to pay attention to the harmfulness of weedy rice and adopt comprehensive control strategies.
Weedy rice (WR) ( Oryza sativa L.) is the most troublesome weed infesting rice paddies in Brazil. Several changes have occurred in this region regarding crop management, especially WR control based on the Clearfield™ (CL) Rice Production System launched in 2003. This survey’s objective was to evaluate the WR infestation status by assessing the producers’ perception and the management practices used in southern Brazil after eighteen years of CL use in Brazil. Rice consultants and extension agents distributed a questionnaire with 213 producers in the Rio Grande do Sul (RS) and Santa Catarina (SC) state in the 2018/19 growing season. In RS, most farms are larger than 150 ha, farmers use minimal or conventional tillage, permanent flooding, adopted the CL system for more than two years, use clomazone PRE tank-mixed with glyphosate at the rice spiking stage, and use crop rotation with soybean [ Glycine max (L.) Merr.] or pasture. In SC, rice farms are small, averaging from 20 to 30 ha, farmers predominantly plant pre-germinated rice and do not rotate rice with other crops and roguing is practiced. Comparing both states, the CL System is used in 99.5, and 69.3% of the total surveyed rice area in RS and SC, respectively. Imidazolinone-resistant WR is present in 68.4 and 26.6% of rice farms in RS and SC, respectively. Rice cultivation in Brazil is currently coexisting with WR with minimal integration of control methods. However, integrated practices can control this weed and are fundamental to the sustainability of systems based on herbicide-resistant rice cultivars.
