Grain-filling Stage Research Articles

Exogeneous selenium enhances anthocyanin synthesis during grain development of colored-grain wheat

Anthocyanins and selenium (Se) play critical roles in antioxidant, anticancer, antibacterial, and antiviral treatments. Previous studies indicate that colored-grain wheat accumulates more Se than regular wheat, and Se synergistically promotes anthocyanin synthesis. However, the mechanism through which Se regulates anthocyanin synthesis remains unclear. We studied anthocyanin accumulation during the grain-filling stage of colored-grain wheat development by employing transcriptomics and metabolomics. We show that Se biofortification increased the concentrations of Se, anthocyanin, chlorophyll a and b, and carotenoids in colored-grain wheat. Genes related to biosynthesis of anthocyanins, phenylpropanoids biosynthesis, and flavonoids biosynthesis were significantly upregulated after Se treatment, which led to the accumulation of anthocyanin metabolites in colored-grain wheat. Genetic alterations in the expression profiles of several genes and transcription factors were observed, which slowed down lignin and proanthocyanidin biosynthesis and accelerated anthocyanin synthesis. Our results deepen the understanding of anthocyanin metabolism in Se-treated colored-grain wheat, which will likely promote harvest of these varieties.

FGW1, a protein containing DUF630 and DUF632 domains, regulates grain size and filling in Oryza sativa L.

Grain filling influences grain size and quality in cereal crops. The molecular mechanisms that regulate grain endosperm development remain elusive. In this study, we characterized a filling-defective and grain width mutant, fgw1, whose mutation increased rice seed width mainly via cell division and expansion in grains. Sucrose contents were higher but starch contents lower in the fgw1 mutant during the grain-filling stage, resulting in inferior endosperm of opaque, white appearance with loosely packed starch granules. Map-based cloning revealed that FGW1 encoded a protein containing DUF630/DUF632 domains, localized in the plasma membrane with preferential expression in the panicle. RNA interference in FGW1 resulted in increased grain width and weight, whereas overexpression of FGW1 led to slightly narrower kernels and better grain filling. In a yeast two-hybrid assay, FGW1 interacted directly with the 14–3–3 protein GF14f, bimolecular fluorescence complementation verified that the site of interaction was the membrane, and the mutated FGW1 protein failed to interact with GF14f. The expression of GF14f was down-regulated in fgw1, and the activities of AGPase, StSase, and SuSase in the endosperm of fgw1 increased similarly to those of a reported GF14f-RNAi. Transcriptome analysis indicated that FGW1 also regulates cellular processes and carbohydrate metabolism. Thus, FGW1 regulated grain formation via the GF14f pathway.

Application of UAV RGB Images and Improved PSPNet Network to the Identification of Wheat Lodging Areas

As one of the main disasters that limit the formation of wheat yield and affect the quality of wheat, lodging poses a great threat to safety production. Therefore, an improved PSPNet (Pyramid Scene Parsing Network) integrating the Normalization-based Attention Module (NAM) (NAM-PSPNet) was applied to the high-definition UAV RGB images of wheat lodging areas at the grain-filling stage and maturity stage with the height of 20 m and 40 m. First, based on the PSPNet network, the lightweight neural network MobileNetV2 was used to replace ResNet as the feature extraction backbone network. The deep separable convolution was used to replace the standard convolution to reduce the amount of model parameters and calculations and then improve the extraction speed. Secondly, the pyramid pool structure of multi-dimensional feature fusion was constructed to obtain more detailed features of UAV images and improve accuracy. Then, the extracted feature map was processed by the NAM to identify the less significant features and compress the model to reduce the calculation. The U-Net, SegNet and DeepLabv3+ were selected as the comparison models. The results show that the extraction effect at the height of 20 m and the maturity stage is the best. For the NAM-PSPNet, the MPA (Mean Pixel Accuracy), MIoU (Mean Intersection over Union), Precision, Accuracy and Recall is, respectively, 89.32%, 89.32%, 94.95%, 94.30% and 95.43% which are significantly better than the comparison models. It is concluded that NAM-PSPNet has better extraction performance for wheat lodging areas which can provide the decisionmaking basis for severity estimation, yield loss assessment, agricultural operation, etc.

Don't panic any more: MORE PANICLES 3 increases rice yield at elevated CO2 levels.

Don't panic any more: MORE PANICLES 3 increases rice yield at elevated CO2 levels.

Agronomic bio-fortification of wheat (Triticum aestivum L.) to alleviate zinc deficiency in human being.

Worldwide, 40% population consumes wheat (Triticum aestivum L.) as a staple food that is low in zinc (Zn) content. Zn deficiency is a major micronutrient disorder in crop plants and humans worldwide, adversely impacting agricultural productivity, human health and socio-economic concern. Globally, the entire cycle of increasing the Zn concentration in wheat grains and its ultimate effect on grain yield, quality, human health & nutrition and socio-economic status of livelihood is less compared. So the present studies were planned to compare the worldwide studies for the alleviation of Zn malnutrition. Zn intake is affected by numerous factors from soil to crop, crop to food and food to humans. The post-harvest fortification, diversification in dietary habits, mineral supplementation and biofortification are various possible approaches to enhance the Zn concentration in food. The wheat grains Zn is influenced by the Zn application technique and time concerning crop developmental stages. The use of soil microorganisms mobilize unavailable Zn, and improve Zn assimilation, plant growth, yield and Zn content in wheat. Climate change can have an inverse impact on the efficiency of agronomic biofortification methods due to a reduction in grain-filling stages. Agronomic biofortification can improve Zn content, crop yield as well as quality and ultimately, have a positive impact on human nutrition, health and socioeconomic status of livelihood. Though bio-fortification research has progressed, some crucial areas are still needed to be addressed or improved to achieve the fundamental purpose of agronomic biofortification.

Influence mechanism of awns on wheat grain Pb absorption: Awns' significant contribution to grain Pb was mainly originated from their direct absorption of atmospheric Pb at the late grain-filling stage

The spike is the organ that contributes the most to lead (Pb) accumulation in wheat grains. However, as an important photosynthetic and transpiration tissue in spike, the role of awn in wheat grain Pb absorption remains unknown. A field experiment was conducted to investigate the influence mechanism of awn on grain Pb accumulation through two comparative treatments: with and without awns (de-awned treatment). The de-awned treatment decreased wheat yield by 4.1 %; however, it significantly lowered the grain Pb accumulation rate at the late filling stage (15 days after anthesis) and led to a 22.8 % decrease in grain Pb concentration from 0.57 to 0.44 mg·kg-1. Moreover, the relative contribution of awn-to-grain Pb accumulation gradually increased with the filling process, finally reaching 26.6 % at maturity. In addition, Pb isotope source analysis indicated that the Pb in the awn and grain mainly originated from atmospheric deposition, and the de-awned treatment decreased the proportion of grain Pb from atmospheric deposition by 8.9 %. Microstructural observations further confirmed that the contribution of awns to grain Pb accumulation mainly originated from their direct absorption of atmospheric Pb. In conclusion, awns play an important role in wheat grain Pb absorption at the late grain-filling stage; planting awnless or short-awn wheat varieties may be the simplest and effective environmental management measure to reduce the health risks of Pb in wheat in regions with serious atmospheric Pb contamination.

Identification and characterization of the chalkiness endosperm gene CHALK-H in rice (Oryza sativa L.)

Chalkiness is one of the most important agronomic traits in rice breeding, which directly affects the quality of rice seed. In this study, we identified a chalkiness endosperm mutant, chalk-h, from N-methyl-N-nitrosourea (MNU)-induced japonica rice cultivar Hwacheong (HC). Compared with wild type (WT)-HC, chalk-h showed severe chalkiness in the endosperm, yellowish green leaves, as well as reduced plant height. Scanning electron microscopy (SEM) analysis showed that starch grains in the chalk-h mutant were irregular in size and loosely arranged, with large gaps between granules, forming ovoid or orbicular shapes. MutMap analysis revealed that the phenotype of chalk-h is controlled by a single recessive gene LOC_Os11g39670 encoding seryl-tRNA synthetase, which is renamed as CHALK-H. A point mutation occurs in chalk-h on the sixth exon (at nucleotide 791) of CHALK-H, in which adenine (A) is replaced by thymidine (T), resulting in an amino acid codon change from glutamine (Glu) to valine (Val). The chalk-h mutant exhibited a heat-sensitive phenotype from the 3-leaf stage, including yellow-green leaves and reduced pigment content. The transcriptional expression of starch synthesis-related genes was down-regulated in the chalk-h mutants compared to WT-HC at different grain-filling stages. With an increase in temperature, the expression of photosynthesis-related genes was down-regulated in the chalk-h mutant compared to WT-HC. Overexpression of CHALK-H rescued the phenotype of chalk-h, with endosperm and leaf color similar to those of WT-HC. Our findings reveal that CHALK-H is a causative gene controlling chalkiness and leaf color of the chalk-h mutant. CHALK-H is the same gene locus as TSCD11, which was reported to be involved in chloroplast development under high temperature. We suggest that CHALK-H/TSCD11 plays important roles not only in chloroplast development, but also in photosynthesis and starch synthesis during rice growth and development, so it has great application potential in rice breeding for high quality and yield.

Biochar Amendment Increases C and N Retention in the Soil–Plant Systems: Its Implications in Enhancing Plant Growth and Water-Use Efficiency Under Reduced Irrigation Regimes of Maize (Zea mays L.)

Biochar influences soil biophysicochemical processes and nutrient availability, yet the effects of different biochar and soil water dynamics on carbon (C) and nitrogen (N) retention in the soil–plant systems remain unknown. Maize plants were grown in split-root pots filled with clay loam soil amended with wheat straw pellet biochar (WSP) and softwood pellet biochar (SWP) at 2% (w/w) and were either irrigated daily to 90% of water-holding capacity (FI) or irrigated with 70% volume of water used for FI to the whole root-zone (DI) or alternately to half root-zone (PRD) from the fourth leaf to grain-filling stage. Compared to the unamended controls, biochar amendment enhanced plant biomass and water-use efficiency, particularly when combined with PRD. Although the WSP amendment tended to decrease soil net N mineralization rate, it significantly increased C and N retention in the soil–plant systems. Compared to DI, PRD significantly increased soil respiration rate while lowering soil total organic C content. Moreover, PRD increased soil inorganic N content, which might be related to increased mineralization of soil organic C (SOC) and soil organic N (SON). Such effects might implicate that PRD outperformed DI in enhancing the mineralization of soil organic matter. Although PRD alone might not be a sustainable irrigation method because of greater C and N losses, biochar addition could alleviate these undesirable effects via depressing SOC and SON mineralization. Biochar amendment, especially WSP combined with PRD, could be a promising practice to increase maize growth and water-use efficiency while sustaining C and N retention in the soil–plant systems.

Fine mapping and validation of a stable QTL for thousand-kernel weight in wheat (Triticum aestivum L.)

Thousand-kernel weight (TKW) is a measure of grain weight, a target of wheat breeding. The object of this study was to fine-map a stable quantitative trait loci (QTL) for TKW and identify its candidate gene in a recombinant inbred line (RIL) population derived from the cross of Kenong 9204 (KN9204) and Jing 411 (J411). On a high-density genetic linkage map, 24, 26 and 25 QTL were associated with TKW, kernel length (KL), and kernel width (KW), respectively. A major and stable QTL, QTkw-2D, was mapped to an 8.3 cM interval on chromosome arm 2DL. By saturation of polymorphic markers in its target region, QTkw-2D was confined to a 9.13 Mb physical interval using a secondary mapping population derived from a residually heterozygous line (F6:7). This interval was further narrowed to 2.52 Mb using QTkw-2D near-isogenic lines (NILs). NILsKN9204 had higher fresh and dry weights than NILsJ411 at various grain-filling stages. The TKW and KW of NILsKN9204 were much higher than those of NILsJ411 in field trials. By comparison of both DNA sequence and expression between KN9204 and J411, TraesCS2D02G460300.1 (TraesKN2D01HG49350) was assigned as a candidate gene for QTkw-2D. This was confirmed by RNA sequencing (RNA-seq) of QTkw-2D NILs. These results provide the basis of map-based cloning of QTkw-2D, and DNA markers linked to the candidate gene may be used in marker-assisted selection.

Oat AsDA1-2D enhances heat stress tolerance and negatively regulates seed-storage globulin

The importance of oats has increased because of their high nutritional value and health benefits in the human diet. High-temperature stress during the reproductive growth period has a detrimental effect on grain morphology by changing the structure and concentration of several seed-storage proteins. DA1, a conserved ubiquitin-proteasome pathway component, plays an important role in regulating grain size by controlling cell proliferation in maternal integuments during the grain-filling stage. However, there have been no reports or studies on oat DA1 genes. In this study, we identified three DA1-like genes (AsDA1-2D, AsDA1-5A, and AsDA1-1D) using genome-wide analysis. Among these, AsDA1-2D was found to be responsible for high-temperature stress tolerance via a yeast thermotolerance assay. The physical interaction of AsDA1-2D with oat-storage-globulin (AsGL-4D) and a protease inhibitor (AsPI-4D) was observed using yeast two-hybrid screening. A subcellular localization assay revealed that AsDA1-2D and its interacting proteins are localized in the cytosol and plasma membrane. An in vitro pull-down assay showed that AsDA1-2D forms a complex with both AsPI-4D and AsGL-4D. An in vitro cell-free degradation assay showed that AsGL-4D was degraded by AsDA1-2D under high-temperature conditions and that AsPI-4D inhibited the function of AsDA1-2D. These results suggest that AsDA1-2D acts as a cysteine protease and negatively regulates oat-grain-storage-globulin under heat stress.

Effects of Post-Anthesis High-Temperature Stress on Carbon Partitioning and Starch Biosynthesis in a Spring Wheat (Triticum aestivum L.) Adapted to Moderate Growth Temperatures.

This study investigates carbon partitioning in the developing endosperm of a European variety of spring wheat subjected to moderately elevated daytime temperatures (27°C/16°C d/night) from anthesis to grain maturity. Elevated daytime temperatures caused significant reductions in both fresh and dry weights and reduced the starch content of harvested grains compared to plants grown under a 20°C/16°C d/night regimen. Accelerated grain development caused by elevated temperatures was accounted for by representing plant development as thermal time (°C DPA). We examined the effects of high-temperature stress (HTS) on the uptake and partitioning of [U-14C]-sucrose supplied to isolated endosperms. HTS caused reduced sucrose uptake into developing endosperms from the second major grain-filling stage (approximately 260°C DPA) up to maturity. Enzymes involved in sucrose metabolism were unaffected by HTS, whereas key enzyme activities involved in endosperm starch deposition such as ADP-glucose pyrophosphorylase and soluble isoforms of starch synthase were sensitive to HTS throughout grain development. HTS caused a decrease in other major carbon sinks such as evolved CO2, ethanol-soluble material, cell walls and protein. Despite reductions in the labeling of carbon pools caused by HTS, the relative proportions of sucrose taken up by endosperm cells allocated to each cellular pool remain unchanged, except for evolved CO2, which increased under HTS and may reflect enhanced respiratory activity. The results of this study show that moderate temperature increases can cause significant yield reductions in some temperate wheat cultivars chiefly through three effects: reduced sucrose uptake by the endosperm, reduced starch synthesis and increased partitioning of carbon into evolved CO2.

Significant difference in the efficacies of silicon application regimes on cadmium species and environmental risks in rice rhizosphere

Silicon (Si) is commonly applied as base-fertilizer or foliar-topdressing to palliate the uptake-translocation-accumulation of cadmium (Cd) in rice through Si–Cd antagonism. However, little is known about the fate of Cd in rice rhizosphere soil and its eco-environmental effects under different Si treatments. Here, systematic works had been carried out to elucidate the Cd species, soil properties, and environmental risks in rice rhizosphere driven by different Si soil-fertilization regimes including CK (without Si-addition), TSi (added before transplanting stage), JSi (added at jointing stage), and TJSi (split into two equal parts, added half before transplanting and another half at jointing stage). Results showed that TJSi outperformed the rest of fertilization regimes. The solid-phase-Cd concentrations treated with TSi, TJSi and JSi were increased by 4.18%, 5.73% and 3.41%, respectively, when compared to CK. The labile Cd (F1+F2) proportion of TJSi was reduced by 16.30%, 9.30% and 6.78%, respectively, when compared to CK, TSi, and JSi. Simultaneously, the liquid-phase-Cd concentration was appreciably suppressed by TJSi throughout the rice lifecycle, while TSi mainly abated Cd dissociation during the vegetative period, and JSi attenuated it during the grain-filling stage. The mobility factor of Cd treated with TJSi was the lowest, which was significantly lower than that of TSi (9.30%) and JSi (6.78%), respectively. Similarly, the oral exposure risk of TJSi was reduced by 4.43% and 32.53%; and the food-chain exposure risk of TJSi was decreased by 13.03% and 42.78%. Additionally, TJSi was the most effective in promoting enzyme activities and nutrient content in rhizosphere soil. Overall, TJSi is more positive and sustainable than TSi and JSi in reconstructing Cd-contaminated rhizosphere environments and abating the environmental risks of Cd. Agronomic practices in Cd-contaminated paddy soils can be informed by applying Si-fertilizer separately before transplanting and at jointing stage to achieve soil welfare and food security.

Rapid and Nondestructive Evaluation of Wheat Chlorophyll under Drought Stress Using Hyperspectral Imaging.

Chlorophyll drives plant photosynthesis. Under stress conditions, leaf chlorophyll content changes dramatically, which could provide insight into plant photosynthesis and drought resistance. Compared to traditional methods of evaluating chlorophyll content, hyperspectral imaging is more efficient and accurate and benefits from being a nondestructive technique. However, the relationships between chlorophyll content and hyperspectral characteristics of wheat leaves with wide genetic diversity and different treatments have rarely been reported. In this study, using 335 wheat varieties, we analyzed the hyperspectral characteristics of flag leaves and the relationships thereof with SPAD values at the grain-filling stage under control and drought stress. The hyperspectral information of wheat flag leaves significantly differed between control and drought stress conditions in the 550-700 nm region. Hyperspectral reflectance at 549 nm (r = -0.64) and the first derivative at 735 nm (r = 0.68) exhibited the strongest correlations with SPAD values. Hyperspectral reflectance at 536, 596, and 674 nm, and the first derivatives bands at 756 and 778 nm, were useful for estimating SPAD values. The combination of spectrum and image characteristics (L*, a*, and b*) can improve the estimation accuracy of SPAD values (optimal performance of RFR, relative error, 7.35%; root mean square error, 4.439; R2, 0.61). The models established in this study are efficient for evaluating chlorophyll content and provide insight into photosynthesis and drought resistance. This study can provide a reference for high-throughput phenotypic analysis and genetic breeding of wheat and other crops.

Integrated ATAC-Seq and RNA-Seq Data Analysis to Reveal OsbZIP14 Function in Rice in Response to Heat Stress.

Transcription factors (TFs) play critical roles in mediating the plant response to various abiotic stresses, particularly heat stress. Plants respond to elevated temperatures by modulating the expression of genes involved in diverse metabolic pathways, a regulatory process primarily governed by multiple TFs in a networked configuration. Many TFs, such as WRKY, MYB, NAC, bZIP, zinc finger protein, AP2/ERF, DREB, ERF, bHLH, and brassinosteroids, are associated with heat shock factor (Hsf) families, and are involved in heat stress tolerance. These TFs hold the potential to control multiple genes, which makes them ideal targets for enhancing the heat stress tolerance of crop plants. Despite their immense importance, only a small number of heat-stress-responsive TFs have been identified in rice. The molecular mechanisms underpinning the role of TFs in rice adaptation to heat stress still need to be researched. This study identified three TF genes, including OsbZIP14, OsMYB2, and OsHSF7, by integrating transcriptomic and epigenetic sequencing data analysis of rice in response to heat stress. Through comprehensive bioinformatics analysis, we demonstrated that OsbZIP14, one of the key heat-responsive TF genes, contained a basic-leucine zipper domain and primarily functioned as a nuclear TF with transcriptional activation capability. By knocking out the OsbZIP14 gene in the rice cultivar Zhonghua 11, we observed that the knockout mutant OsbZIP14 exhibited dwarfism with reduced tiller during the grain-filling stage. Under high-temperature treatment, it was also demonstrated that in the OsbZIP14 mutant, the expression of the OsbZIP58 gene, a key regulator of rice seed storage protein (SSP) accumulation, was upregulated. Furthermore, bimolecular fluorescence complementation (BiFC) experiments uncovered a direct interaction between OsbZIP14 and OsbZIP58. Our results suggested that OsbZIP14 acts as a key TF gene through the concerted action of OsbZIP58 and OsbZIP14 during rice filling under heat stress. These findings provide good candidate genes for genetic improvement of rice but also offer valuable scientific insights into the mechanism of heat tolerance stress in rice.

Shading affects the starch structure and digestibility of wheat by regulating the photosynthetic light response of flag leaves

Heavy haze-induced decreases in solar radiation represent an important factor that affects the structural properties of starch macromolecules. However, the relationship between the photosynthetic light response of flag leaves and the structural properties of starch remains unclear. In this study, we investigated the impact of light deprivation (60 %) during the vegetative-growth or grain-filling stage on the leaf light response, starch structure, and biscuit-baking quality of four wheat cultivars with contrasting shade tolerance. Shading decreased the apparent quantum yield and maximum net photosynthetic rate of flag leaves, resulting in a lower grain-filling rate and starch content and higher protein content. Shading decreased the starch, amylose, and small starch granule amount and swelling power but increased the larger starch granule amount. Under shade stress, the lower amylose content decreased the resistant starch content while increasing the starch digestibility and estimated glycemic index. Shading during the vegetative-growth stage increased starch crystallinity, 1045/1022 cm−1 ratio, starch viscosity, and the biscuit spread ratio, while shading during the grain-filling stage decreased these values. Overall, this study indicated that low light affects the starch structure and biscuit spread ratio by regulating the photosynthetic light response of flag leaves.

Light intensity-mediated auxin homeostasis in spikelets links carbohydrate metabolism enzymes with grain filling rate in rice.

Low light (LL) stress during the grain-filling stage acutely impairs the quality and quantity of starch accumulation in rice grains. Here, we observed that LL-induced poor starch biosynthesis is modulated by auxin homeostasis, which regulates the activities of major carbohydrate metabolism enzymes such as starch synthase (SS) and ADP-glucose pyrophosphorylase (AGPase) in rice. Further, during the grain-filling period under LL, the starch/sucrose ratio increased in leaves but significantly decreased in the developing spikelets. This suggests poor sucrose biosynthesis in leaves and starch in the grains of the rice under LL. A lower grain starch was found to be correlated with the depleted AGPase and SS activities in the developing rice grains under LL. Further, under LL, the endogenous auxin (IAA) level in the spikelets was found to be synchronized with the expression of a heteromeric G protein gene, RGB1. Interestingly, under LL, the expression of OsYUC11 was significantly downregulated, which subsequently resulted in reduced IAA in the developing rice spikelets, followed by poor activation of grain-filling enzymes. This resulted in lowered grain starch accumulation, grain weight, panicle number, spikelet fertility, and eventually grain yield, which was notably higher in the LL-susceptible (GR4, IR8) than in the LL-tolerant (Purnendu, Swarnaprabha) rice genotypes. Therefore, we hypothesize that depletion in auxin biosynthesis under LL stress is associated with the downregulation of RBG1, which discourages the expression and activities of grain-filling enzymes, resulting in lower starch production, panicle formation, and grain yield in rice.

Within-leaf chloroplasts and nitrogen allocation to thylakoids in relation to photosynthesis during grain filling in maize

Nitrogen (N) is an important contributor to photosynthetic rate (Pn). However, during grain-filling stage in maize, some leaf N is remobilized to meet demands for grain protein accumulation rather than photosynthetic demands. Therefore, plants that can maintain a relatively high Pn during the N remobilization process would have the key to achieving both high grain yields (HGY) and high grain protein concentrations (HGPC). In this study, we investigated two high-yielding maize hybrids in photosynthetic apparatus and N allocation in a two-year field experiment. During grain filling, XY335 had a higher Pn and photosynthetic N-use efficiency than ZD958 had in the upper leaf, but not in the middle or lower leaves. In the upper leaf, the diameter and area of the bundle sheath (BS) were larger and the distance between bundle sheaths was greater in XY335 than in ZD958. XY335 had more bundle sheath cells (BSCs) and a larger BSC area, as well as a larger chloroplast area in the BSC, resulting in a higher total number and total area of chloroplasts in the BS. XY335 also had higher stomatal conductance (gs), intercellular CO2 concentration, and N allocation to the thylakoids. No genotypic differences were found in mesophyll cell ultrastructure, N content and starch content in the three types of leaves. Therefore, a trifecta of higher gs, greater N allocation to thylakoids for photo-phosphorylation and electron transport, and more and larger chloroplasts promoting CO2 assimilation in the BS confers a high Pn to simultaneously achieve HGY and high HGPC in maize.

Different characteristics of soil CH4 emissions and methanogenic communities in paddy fields under gradually and abruptly elevated CO2 concentrations

Studying methanogenesis in paddy fields under future climate change scenarios is important for carbon sequestration and reduction in agroecosystems. Most studies have investigated the effects of elevated CO2 concentrations (e[CO2]) on CH4 emissions in paddy fields under a constant CO2 concentration ([CO2]). However, the increase in the [CO2] in the atmosphere is a gradual process rather than an abrupt increase, and the [CO2] in the atmosphere has remained high and relatively constant. In this research, we explored the differences in methanogenesis in paddy fields under gradually and abruptly e[CO2] using open-top chambers (OTCs). CH4 flux, soil physicochemical properties, enzyme activities, methane production potential (MPP), and methanogenic (mcrA gene) characteristics were analyzed under CK (ambient [CO2]), C1 (gradually e[CO2] by 200 μmol mol−1), and C2 (abruptly e[CO2] by 200 μmol mol−1) treatments. The results showed that the C1 and C2 treatments significantly promoted the cumulative amount of CH4 emissions (CAC) by 63.3% and 86.5%, respectively, and significantly increased the CAC/yield by 30.8% and 47.3%, respectively, compared with the CK treatment. In addition, the C1 and C2 treatments increased the DOC concentration, enzyme activities (urease, invertase, and catalase), MPP, and mcrA gene abundance in paddy soils. Notably, CAC/yield, shoot biomass, and soil seasonal average urease activity under the C2 treatment were increased by 12.6%, 12.2%, and 3.0%, respectively, compared with those in C1. The methanogenic activity of the C2 treatment was significantly increased by 24.1% and 24.4% during the tillering and grain-filling stages, respectively, and the methanogenic abundance of the C2 treatment was significantly increased by 53.9% and 72.2% during the tillering and elongation stages, respectively, compared with that of C1. Therefore, it is inappropriate to ignore the fact that [CO2] increases gradually and to only examine the effects of high e[CO2] on agroecosystems.

Effects of Warming and Drought Stress on the Coupling of Photosynthesis and Transpiration in Winter Wheat (Triticum aestivum L.)

The coupling of photosynthesis and transpiration in plant leaves forms the basis of carbon–water coupling in terrestrial ecosystems. Previous studies have attributed the coupling of leaf photosynthesis and transpiration to joint stomata control, but they lack analyses of the coupling mechanism. In this study, winter wheat (Triticum aestivum L.) was selected as a plant material on the North China Plain. Under the conditions of warming and drought stress, the photosynthetic rate (An), transpiration rate (Tr), water pressure saturation (VPD), and leaf temperature (T1) of wheat were recorded on clear days at the jointing, flowering, and grain-filling stages from 9:00 to 12:00 a.m. Then, the measured values were fitted to the simulated values obtained using the Ball–Berry and Penman–Monteith models. The results showed that the stomatal size, stomatal conductance, An, and Tr of winter wheat leaves were decreased by warming, drought stress, and their synergistic effects. Based on the Ball–Berry model, different fitting effects were observed in the treatments of adequate water supply with warming (R-g), water deficit with warming (R-d), adequate water supply without warming (N-g), and water deficit without warming (N-d). The R2 values of the R-g, R-d, N-g, and N-d treatments were 0.962, 0.958, 0.964, and 0.943, respectively. The Tr values were fitted based on the Penman–Monteith model. In the R-g, R-d, N-g, and N-d treatments, the R2 values of the R-g, R-d, N-g, and N-d treatments were 0.923, 0.849, 0.934, and 0.919, respectively. In conclusion, both warming and water deficit reduce stomatal conductance, An, Tr, and the coupling effect of photosynthesis and transpiration.

An analysis of sugary endosperm in sorghum: Characterization of mutant phenotypes depending on alleles of the corresponding starch debranching enzyme.

Sorghum is the fifth most important cereal crop. Here we performed molecular genetic analyses of the 'SUGARY FETERITA' (SUF) variety, which shows typical sugary endosperm traits (e.g., wrinkled seeds, accumulation of soluble sugars, and distorted starch). Positional mapping indicated that the corresponding gene was located on the long arm of chromosome 7. Within the candidate region of 3.4 Mb, a sorghum ortholog for maize Su1 (SbSu) encoding a starch debranching enzyme ISA1 was found. Sequencing analysis of SbSu in SUF uncovered nonsynonymous single nucleotide polymorphisms (SNPs) in the coding region, containing substitutions of highly conserved amino acids. Complementation of the rice sugary-1 (osisa1) mutant line with the SbSu gene recovered the sugary endosperm phenotype. Additionally, analyzing mutants obtained from an EMS-induced mutant panel revealed novel alleles with phenotypes showing less severe wrinkles and higher Brix scores. These results suggested that SbSu was the corresponding gene for the sugary endosperm. Expression profiles of starch synthesis genes during the grain-filling stage demonstrated that a loss-of-function of SbSu affects the expression of most starch synthesis genes and revealed the fine-tuned gene regulation in the starch synthetic pathway in sorghum. Haplotype analysis using 187 diverse accessions from a sorghum panel revealed the haplotype of SUF showing severe phenotype had not been used among the landraces and modern varieties. Thus, weak alleles (showing sweet and less severe wrinkles), such as in the abovementioned EMS-induced mutants, are more valuable for grain sorghum breeding. Our study suggests that more moderate alleles (e.g. produced by genome editing) should be beneficial for improving grain sorghum.