Integrating C4 photosynthesis into C3 crops to increase yield potential

The growth rate of the human population is faster than improvements in crop yields. To feed people in the future, multiple strategies are required. One proposed approach is to raise the yield potential of C(3) crops by modifying photosynthesis to the more efficient C(4) pathway. Owing to complex changes associated with C(4) photosynthesis, it is no understatement to define this conversion as one of the Grand Challenges for Biology in the 21st Century. Here we outline the challenges of installing a C(4) system and assess how new approaches and knowledge may help achieve this goal.     

Physiological traits contributed to the recent increase in yield potential of winter wheat from Henan Province,China

This experiment aims to test the traits responsible for the increase in yield potential of winter wheat released in Henan Province, China. Seven established cultivars released in the last 20 years and three advanced lines were assayed. The results showed that grain yield was positively correlated with harvest index(HI), kernel number per square meter, and aboveground biomass. In addition, the HI and aboveground biomass showed an increasing trend with the year of release.Therefore, we can conclude that bread wheat breeding advances during recent decades in Henan Province, China,have been achieved through an increase in HI, kernel number per square meter, and aboveground biomass. A higher d13C seems also to be involved in these advances, which suggests a progressive improvement in constitutive water use efficiency not associated with a trend towards lower stomatal conductance in the most recent genotypes. However, genetic advance Researchdoes not appear related to changes in photosynthesis rates on area basis when measured in the flag leaf or the spike,but only to a higher, whole‐spike photosynthesis. Results also indirectly support the concept that under potential yield conditions, the spike contributed more than the flag leaf to kernel formation.     

Physiological traits contributed to the recent increase in yield potential of winter wheat from Henan Province,China

This experiment aims to test the traits responsible for the increase in yield potential of winter wheat released in Henan Province, China. Seven established cultivars released in the last 20 years and three advanced lines were assayed. The results showed that grain yield was positively correlated with harvest index（HI）, kernel number per square meter, and aboveground biomass. In addition, the HI and aboveground biomass showed an increasing trend with the year of release.Therefore, we can conclude that bread wheat breeding advances during recent decades in Henan Province, China,have been achieved through an increase in HI, kernel number per square meter, and aboveground biomass. A higher d13C seems also to be involved in these advances, which suggests a progressive improvement in constitutive water use efficiency not associated with a trend towards lower stomatal conductance in the most recent genotypes. However, genetic advance Researchdoes not appear related to changes in photosynthesis rates on area basis when measured in the flag leaf or the spike,but only to a higher, whole‐spike photosynthesis. Results also indirectly support the concept that under potential yield conditions, the spike contributed more than the flag leaf to kernel formation.     

Bioenergy from plants and the sustainable yield challenge

Bioenergy from plants, particularly from perennial grasses and trees, could make a substantial contribution to alleviation of global problems in climate change and energy security if high yields can be sustained. Here, yield traits in a range of key bioenergy crops are reviewed, from which several targets for future improvement can be identified. Some are already the focus of genetically modified (GM) and non-GM approaches. However, the efficient growth strategies of perennial bioenergy crops rely on newly assimilated and recycled carbon and remobilized nitrogen in a continually shifting balance between sources and sinks. This balance is affected by biotic (e.g. pest, disease) and abiotic (e.g. drought) stresses. Future research should focus on three main challenges: changing (photo)thermal time sensitivity to lengthen the growing season without risking frost damage or limiting remobilization of nutritional elements following senescence; increasing aboveground biomass without depleting belowground reserves required for next year's growth and thus without increasing the requirement for nutrient applications; and increasing aboveground biomass without increasing water use.     

Using C4 photosynthesis to increase the yield of rice-rationale and feasibility

90% of the world's rice is grown and consumed in Asia, with each hectare of rice-producing land providing food for 27 people. By 2050, because of population growth and increasing urbanisation, each remaining hectare will have to feed at least 43 people. This means that yields must be increased by at least 50% over the next 40 years to prevent mass malnutrition for the 700 million Asians that currently rely on rice for more than 60% of their daily calorific intake. Since predictive models suggest that yield increases of this magnitude can only be achieved by improving photosynthesis, and because evolution has increased photosynthetic efficiency by 50% in the form of the C4 pathway, one solution is to generate C4 rice. However, this is an ambitious goal that requires proof of concept before any major investment of time and money. Here, we discuss approaches that should allow proof of concept to be tested.     

Crop yield response to climate change varies with cropping intensity

Projections of the response of crop yield to climate change at different spatial scales are known to vary. However, understanding of the causes of systematic differences across scale is limited. Here, we hypothesize that heterogeneous cropping intensity is one source of scale dependency. Analysis of observed global data and regional crop modelling demonstrate that areas of high vs. low cropping intensity can have systematically different yields, in both observations and simulations. Analysis of global crop data suggests that heterogeneity in cropping intensity is a likely source of scale dependency for a number of crops across the globe. Further crop modelling and a meta‐analysis of projected tropical maize yields are used to assess the implications for climate change assessments. The results show that scale dependency is a potential source of systematic bias. We conclude that spatially comprehensive assessments of climate impacts based on yield alone, without accounting for cropping intensity, are prone to systematic overestimation of climate impacts. The findings therefore suggest a need for greater attention to crop suitability and land use change when assessing the impacts of climate change.     

Pooling hair samples to increase DNA yield for PCR

Hairs are useful non-invasive sources of DNA, but the DNA yield can be very small, thus promoting genotyping errors. Using multiple hairs can counter this problem, but may introduce multiple contributors to a sample if collected remotely. With microsatellite genotyping, samples representing multiple animals are obvious if three or more alleles are detected at any locus: these samples can then be removed from any analyses. However, some multiple-individual samples may have only one or two alleles at each of the loci examined. We investigated the probability of failing to identify mixed pooled samples by simulating pooled samples (10 000 replicates) from microsatellite data from the northern and southern hairy-nosed wombats (NHNW, Lasiorhinus krefftii; SHNW, L. latifrons), species with low and high genetic diversity respectively. The majority (81.7%) of the 40 000 simulated samples had three or four alleles, so were readily identified as mixed. In the remaining 1-or-2-allele SHNW samples, forensic science software (DNAMIX) correctly identified mixed versus single-individual samples for all cases when the probability of locus failure was low (P _(LF) = 0.1), and 99% of samples when locus failure was high (P _(LF) = 0.5). For NHNW however, the probability of failing to identify a mixed sample was too high for population size estimation (0.05), even when the probability of locus failure was low. In cases such as this, pooled samples may be adequate for less demanding tasks, such as estimation of allele proportions. However, for animal populations with at least average levels of genetic variation, pooling of samples could safely be utilised for most applications. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of interspecies hybrids to increase ginseng biomass and ginsenoside yield

Key message

Interspecific hybrids between Panax ginseng and P. quinquefolius results in hybrid vigor and higher ginsenoside contents.

Abstract

Ginseng is one of the most important herbs with valued pharmaceutical effects contributing mainly by the presence of bioactive ginsenosides in the roots. However, ginseng industry is impeded largely by its biological properties, because ginseng plants are slow-growing perennial herbs with lower yield. To increase the ginseng yield and amounts of ginsenosides, we developed an effective ginseng production system using the F₁ progenies obtained from the interspecific reciprocal cross between two Panax species: P. ginseng and P. quinquefolius. Although hybrid plants show reduced male fertility, F₁ hybrids with the maternal origin either from P. ginseng or P. quinquefolius displayed heterosis; they had larger roots and higher contents of ginsenosides as compared with non-hybrid parental lines. Remarkably, the F₁ hybrids with the maternal origin of P. quinquefolius had much higher ginsenoside contents, especially ginsenoside Re and Rb1, than those with the maternal origin of P. ginseng. Additionally, non-targeted metabolomic profiling revealed a clear increase of a large number of primary and secondary metabolites including fatty acids, amino acids and ginsenosides in hybrid plants. To effectively identify the F₁ hybrids for the large-scale cultivation, we successfully developed a molecular marker detection system for discriminating F₁ reciprocal hybrids. In summary, this work provided a practical system for reciprocal hybrid ginseng production, which would facilitate the ginseng production in the future.

     

Improving photosynthesis to increase grain yield potential: an analysis of maize hybrids released in different years in China

Photosynthesis Research - In this work, we sought to understand how breeding has affected photosynthesis and to identify key photosynthetic indices that are important for increasing maize yield in...     

Tactic responses to pollutants and their potential to increase biodegradation efficiency

A significant number of bacterial strains are able to use toxic aromatic hydrocarbons as carbon and energy sources. In a number of cases, the evolution of the corresponding degradation pathway was accompanied by the evolution of tactic behaviours either towards or away from these toxic carbon sources. Reports are reviewed which show that a chemoattraction to heterogeneously distributed aromatic pollutants increases the bioavailability of these compounds and their biodegradation efficiency. An extreme form of chemoattraction towards aromatic pollutants, termed ‘hyperchemotaxis’, was described for Pseudomonas putida DOT‐T1E, which is based on the action of the plasmid‐encoded McpT chemoreceptor. Cells with this phenotype were found of being able to approach and of establishing contact with undiluted crude oil samples. Although close McpT homologues are found on other degradation plasmids, the sequence of their ligand‐binding domains does not share significant similarity with that of NahY, the other characterized chemoreceptor for aromatic hydrocarbons. This may suggest the existence of at least two families of chemoreceptors for aromatic pollutants. The use of receptor chimers comprising the ligand‐binding region of McpT for biosensing purposes is discussed.     

Growth yield increase linked to caffeate reduction in Acetobacterium woodii

Growth yields were determined with Acetobacterium woodii strain NZva 16 on hydrogen and CO₂, formate, methanol, vanillate, ferulate and fructose in mineral medium in the absence and presence of 0.05% yeast extract. Yeast extract was not essential for growth but enhanced growth yields by 25–100% depending on the substrate fermented. Comparison of yields on formate or methanol allowed calculation of an energy yield in the range of 1.5–2 mol ATP per mol acetate formed during homoacetate fermentation of A. woodii. In the presence of 6 mM caffeate, growth yields were determined with the substrates formate or methanol. Caffeate was reduced to hydrocaffeate and increased growth yields were obtained. An ATP yield of about 1 mol per mol of caffeate reduced was calculated. Cytochromes were not detectable in cell free extracts or membrane preparations.     

Methodologies to increase the transformation efficiencies and the range of bacteria that can be transformed

Methods for transfer of exogenous DNA into cells are essential for genetics and molecular biology, and the lack of effective methods hampers research on many different species of bacteria which have shown to be particularly recalcitrant to transformation. This review presents the progress on the development of methods for artificial transformation of bacteria with emphasis on different methodologies and the range of bacteria that can be transformed. The methods' strengths and weaknesses are described.     

Novel and potential application of cryopreservation to plant genetic transformation

The world population now is 6.7 billion and is predicted to reach 9 billion by 2050. Such a rapid growing population has tremendously increased the challenge for food security. Obviously, it is impossible for traditional agriculture to ensure the food security, while plant biotechnology offers considerable potential to realize this goal. Over the last 15 years, great benefits have been brought to sustainable agriculture by commercial cultivation of genetically modified (GM) crops. Further development of new GM crops will with no doubt contribute to meeting the requirements for food by the increasing population. The present article provides updated comprehensive information on novel and potential application of cryopreservation to genetic transformation. The major progresses that have been achieved in this subject include (1), long-term storage of a large number of valuable plant genes, which offers a good potential for further development of novel cultivars by genetic transformation; (2), retention of regenerative capacity of embryogenic tissues and protoplasts, which ensures efficient plant regeneration system for genetic transformation; (3), improvement of transformation efficiency and plant regeneration of transformed cells; (4), long-term preservation of transgenic materials with stable expression of transgenes and productive ability of recombinant proteins, which allows transgenic materials to be stored in a safe manner before being analyzed and evaluated, and allows establishment of stable seed stocks for commercial production of homologous proteins. Data provided in this article clearly demonstrate that cryo-technique has an important role to play in the whole chain of genetic transformation. Further studies coupling cryotechnique and genetic transformation are expected to significantly improve development of new GM crops.