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Methane Emissions from Wetlands in China and Their Climate Feedbacks in the 21st Century
No full textWetlands are large sinks of carbon dioxide (CO2) and sources of methane (CH4). Both fluxes can be altered by wetland management (e.g., restoration), leading to changes in the climate system. Here, we use multiple models to assess CH4 emissions and CO2 sequestration from the wetlands in China and the impacts on climate under three climate scenarios and four wetland management scenarios with various levels of wetland restoration in the 21st century. We find that wetland restoration leads to increased CH4 emissions with a national total of 0.32-11.31 Tg yr-1. These emissions induce an additional radiative forcing of 0.0005-0.0075 W m-2 yr-1 and global annual mean air temperature rise of 0.0003- 0.0053 ? yr-1, across all future climate and management scenarios. However, wetland restoration also resulted in net CO2 sequestration, leading to a combined net greenhouse gas sink in all climate management scenarios, except in the highest restoration level combined with the hottest climate scenario. The highest climate cooling was achieved under medium restoration, with the climate scenario consistent with the Paris agreement target of below 2 ?, with a cumulative global warming potential of -3.2 Pg CO2-eq (2020- 2100). Wetland restoration in the Qinghai-Tibet Plateau offers the greatest cooling effect
Phenotypic Characterization of Oryza nivara (Sharma et Shastry) Collected from Different Ecological Niches of Sri Lanka
No full textInformation on the genetic diversity of wild rice species in Sri Lanka is relatively meagre, though it plays a key role in crop improvement programs of cultivated rice (Oryza sativa L.). The present study was carried out to identify the morphological variation pattern of the wild populations of O. nivara in Sri Lanka. Seven populations (P1 to P7) collected from different agro-ecological regions were characterized in a common garden based on nine mor-phological traits. The findings revealed a high level of phenotypic variation between populations when compared to within a population. The most variable traits were the flag leaf panicle neck length (FLPNL) and flag leaf angle (FLA), whereas the least variable trait was the flag leaf length (FLL). Box plots clearly illustrated the large differ-entiation of phenotypic traits in the entire distribution of wild rice populations. The cumulative values of the two principal components, i.e., FLPNL and FLA, explained 58.7% of the total variance. Populations from similar nat-ural habitats clustered together. The P7 was adapted to intercept more sunlight by increasing flag leaf width (FLW) and FLA to compete with weeds and other shrubs. P2 and P5 were the most closely related populations representing approximately similar ecological conditions of the dry zone. The P3 population from the intermedi-ate zone showed a vigorous plant growth with the highest plant height, culm girth and awn length (P < 0.05). Knowledge of such morphological diversity would facilitate designing conservation strategies and basic informa-tion for the proper utilization of wild resources in rice genetic improvement
The methyl-CpG-binding domain family member PEM1 is essential for Ubisch body formation and pollen exine development in rice
No full textPollen exine is composed of finely-organized nexine, bacula and tectum, and is crucial for pollen viability and function. Pollen exine development involves a complicated molecular network that coordinates the interaction between pollen and tapetal cells, as well as the biosynthesis, transport and assembly of sporopollenin precursors; however, our understanding of this network is very limited. Here, we report the roles of PEM1, a member of methyl-CpG-binding domain family, in rice pollen development. PEM1 expressed constitutively and, in anthers, its expression was detectable in tapetal cells and pollen. This predicted PEM1 protein of 240 kDa had multiple epigenetic-related domains. pem1 mutants exhibited abnormal Ubisch bodies, delayed exine occurrence and, finally, defective exine, including invisible bacula, amorphous and thickened nexine and tectum layer structures, and also had the phenotype of increased anther cuticle. The mutation in PEM1 did not affect the timely degradation of tapetum. Lipidomics revealed much higher wax and cutin contents in mutant anthers than in wild-type. Accordingly, this mutation up-regulated the expression of a set of genes implicated in transcriptional repression, signaling and diverse metabolic pathways. These results indicate that PEM1 mediates Ubisch body formation and pollen exine development mainly by negatively modulating the expression of genes. Thus, the PEM1-mediated molecular network represents a route for insights into mechanisms underlying pollen development. PEM1 may be a master regulator of pollen exine development
Arbuscular Mycorrhizal Fungi Compete Asymmetrically for Amino Acids with Native and Invasive Solidago
No full textArbuscular mycorrhizal fungi (AMF) and soil amino acids both affect plant performance. However, little is known about how AMF compete for amino acids with native and invasive congeners. We conducted a factorial experiment (inoculation, native and invasive species, and amino acids) to examine the competition for amino acids between soil microbes and both native and invasive congeners. The competition for amino acids between AMF and invasive Solidago canadensis was weaker than that observed between AMF and native S. decurrens. This asymmetric competition increased the growth advantage of S. canadensis over S. decurrens. The efficacy (biomass production per unit of nitrogen supply) of amino acids compared to ammonium was smaller in S. canadensis than in S. decurrens when both species were grown without inoculation, but the opposite was the case when both species were grown with AMF. AMF and all microbes differentially altered four phenotypic traits (plant height, leaf chlorophyll content, leaf number, and root biomass allocation) and the pathways determining the effects of amino acids on growth advantages. These findings suggest that AMF could enhance plant invasiveness through asymmetric competition for amino acids and that amino acid-driven invasiveness might be differentially regulated by different microbial guilds
Influences of open-central canopy on photosynthetic parameters and fruit quality of apples (Malus x domestica) in the Loess Plateau of China
No full textAlthough open-central canopy (OCC) is popular in apple (Malus x domestica) orchards in Loess Plateau of China, its relevant photosynthetic mechanisms have not been elucidated. In this study, changes in photosynthetically active radiation ( PAR ), gas exchange, chlorophyll fluorescence quenching and fruit quality in apple trees were measured in OCC and compared with those in the conventional condensed round and large canopy (RLC). Results showed that light intercepted at different orientations was 44% higher by OCC than that by RLC. The improved light environment within OCC remarkably increased leaf maximum net photosynthetic rate (P-nmax) and significantly decreased stomatal limitation. Under high light, the ratio of photorespiratory rate to gross photosynthetic rate (P-r/P-g) in OCC was higher than that in RLC. Moreover, reversible component in non-photochemical quenching (r(qE)) was increased, while irreversible component (r(qI)) was decreased in OCC than in RLC. As a result, the fruit quality in OCC was greatly boosted as evidenced by the significantly increased single fruit weight, fruit flesh firmness and fruit soluble solid contents and the sharply decreased fruit titratable acid contents. PAR intercepted by the canopy and the fruit soluble solid contents, leaf P-nmax or single fruit weight were positively correlated, while PAR or P-nmax was negatively correlated with the fruit titratable acid contents. Accordingly, the improved crown light environment and the enhanced leaf photosynthetic performance and photoprotective capacity in OCC led to the boosted fruit quality
An enhancing effect attributed to a nonsynonymous mutation in SOYBEAN SEED SIZE 1, a SPINDLY-like gene, is exploited in soybean domestication and improvement
No full textSoybean (Glycine max) was domesticated from its wild relative Glycine soja. One-hundred-seed weight is one of the most important domesticated traits determining soybean yield; however, its underlying genetic basis remains elusive. We characterized a soybean seed size 1 (sss1) mutant featuring large seeds compared to its wild-type background. Positional cloning revealed that the candidate gene GmSSS1 encoded a SPINDLY homolog and was co-located in a well-identified quantitative trait locus (QTL)-rich region on chromosome 19. Knocking out GmSSS1 resulted in small seeds, while overexpressing GmSSS1/Gmsss1 induced large seeds. Modulating GmSSS1/Gmsss1 in transgenic plants can positively influence cell expansion and cell division. Relative to GmSSS1, one mutation leading to an E to Q substitution at the 182(nd) residue in Gmsss1 conferred an enhancing effect on seed weight. GmSSS1 underwent diversification in wild-type and cultivated soybean, and the alleles encoding the Gmsss1-type substitution of 182(nd)-Q, which originated along the central and downstream parts of the Yellow River, were selected and expanded during soybean domestication and improvement. We cloned the causative gene for the sss1 mutant, which is linked with a seed weight QTL, identified an elite allele of this gene for increasing seed weight, and provided new insights into soybean domestication and breeding
m6A-mediated regulation of crop development and stress responses
No full textDynamic chemical modifications in eukaryotic messenger RNAs (mRNAs) constitute an essential layer of gene regulation, among which N-6-methyladenosine (m(6)A) was unveiled to be the most abundant. m(6)A functionally modulates important biological processes in various mammals and plants through the regulation of mRNA metabolism, mainly mRNA degradation and translation efficiency. Physiological functions of m(6)A methylation are diversified and affected by intricate sequence contexts and m(6)A machineries. A number of studies have dissected the functional roles and the underlying mechanisms of m(6)A modifications in regulating plant development and stress responses. Recently, it was demonstrated that the human FTO-mediated plant m(6)A removal caused dramatic yield increases in rice and potato, indicating that modulation of m(6)A methylation could be an efficient strategy for crop improvement. In this review, we summarize the current progress concerning the m(6)A-mediated regulation of crop development and stress responses, and provide an outlook on the potential application of m(6)A epitranscriptome in the future improvement of crops
Dependence of the rate-limiting steps in the dark-to-light transition of photosystem II on the lipidic environment of the reaction center
No full textIn our earlier works, we have identified rate-limiting steps in the dark-to-light transition of PSII. By measuring chlorophyll a fluorescence transients elicited by single-turnover saturating flashes (STSFs) we have shown that in diuron-treated samples an STSF generates only F-1 (< F-m) fluorescence level, and to produce the maximum (F-m) level, additional excitations are required, which, however, can only be effective if sufficiently long Ar waiting times are allowed between the excitations. Biological variations in the half-rise time (Delta tau(1/2)) of the fluorescence increment suggest that it may be sensitive to the physicochemical environment of PSII. Here, we investigated the influence of the lipidic environment on Delta tau(1/2) of PSII cote complexes of Thermosynechococcus vulcanus. We found that while non-native lipids had no noticeable effects, thylakoid membrane lipids considerably shortened the Delta tau(1/2), from similar to 1 ms to similar to 0.2 ins. The importance of the presence of native lipids was confirmed by obtaining similarly short Delta tau(1/2 )values in the whole T. vulcanus cells and isolated pea thylakoid membranes. Minor, lipid-dependent reorganizations were also observed by steady-state and time-resolved spectroscopic measurements. These data show that the processes beyond the dark-to-light transition of PSII depend significantly on the lipid matrix of the reaction center
Natural variations of ZmSRO1d modulate the trade-off between drought resistance and yield by affecting ZmRBOHC-mediated stomatal ROS production in maize
No full textWhile crop yields have historically increased, drought resistance has become a major concern in the context of global climate change. The trade-off between crop yield and drought resistance is a common phenomenon; however, the underlying molecular modulators remain undetermined. Through genome-wide association study, we revealed that three non-synonymous variants in a drought-resistant allele of ZmSRO1d-R resulted in plasma membrane localization and enhanced mono-ADP-ribosyltransferase activ-ity of ZmSRO1d toward ZmRBOHC, which increased reactive oxygen species (ROS) levels in guard cells and promoted stomatal closure. ZmSRO1d-R enhanced plant drought resilience and protected grain yields under drought conditions, but it led to yield drag under favorable conditions. In contrast, loss-of-function mutants of ZmRBOHC showed remarkably increased yields under well-watered conditions, whereas they showed compromised drought resistance. Interestingly, by analyzing 189 teosinte accessions, we found that the ZmSRO1d-R allele was present in teosinte but was selected against during maize domestication and modern breeding. Collectively, our work suggests that the allele frequency reduction of ZmSRO1d-R in breeding programs may have compromised maize drought resistance while increased yields. Therefore, introduction of the ZmSRO1d-R allele into modern maize cultivars would contribute to food security under drought stress caused by global climate change
Enzymological and structural characterization of Arabidopsis thaliana heme oxygenase-1
No full textArabidopsis thaliana heme oxygenase-1 (AtHO-1), a metabolic enzyme in the heme degradation pathway, serves as a prototype for study of the bilin-related functions in plants. Past biological analyses revealed that AtHO-1 requires ferredoxin-NADP(+) reductase (FNR) and ferredoxin for its enzymatic activity. Here, we characterized the binding and degradation of heme by AtHO-1, and found that ferredoxin is a dispensable component of the reducing system that provides electrons for heme oxidation. Furthermore, we reported the crystal structure of heme-bound AtHO-1, which demonstrates both conserved and previously undescribed features of plant heme oxygenases. Finally, the electron transfer pathway from FNR to AtHO-1 is suggested based on the known structural information