Physiological and comparative proteome analyses reveal low-phosphate tolerance and enhanced photosynthesis in a maize mutant owing to reinforced inorganic phosphate recycling

Assessment of the major biochemical and physiological mechanisms underlying green-synthesised selenium nanoparticles-mediated alleviation of lanthanum toxicity in mung bean (Vigna radiata L.)

The entry of various nanoparticles into environmental compartments and their eventual presence in plant-based foods and humans is inevitable. This study focussed to elucidate the major mechanisms underlying green-synthesised selenium nanoparticles (SeNPs)-mediated control of lanthanum (La) impacts in 30-day-old mung bean (Vigna radiata L.). The foliar application of 0.6 mg/L SeNPs more prominently improved stomatal behaviour, carbohydrate metabolism, growth and photosynthetic characteristics under the absence and presence of 1.5 mM La. Key indicators of oxidative stress and antioxidant metabolism were measured. The leaves from V. radiata receiving SeNPs exhibited increased antioxidant system that helped in inhibiting the La-toxicity by reducing the content of hydrogen peroxide (H2O2) by 58.9 % and thiobarbituric acid reactive substances (TBARS) by 52.0 % in comparison with La-stressed plants. The application of SeNPs promoted overall growth and photosynthetic functions by increasing chlorophyll content by 17.6 %, fresh weight and dry weight by 23.9 % and 25.0 %, respectively, under La stress compared to control. Additionally, the study examined the cellular levels of soluble sugars and starch, and also correlated indicators of antioxidant metabolism with the modulation of key Calvin cycle enzymes. The chloroplast of La-stressed V. radiata had disorganized thylakoids, which were transformed to well-developed thylakoids and stacked grana after foliar application of 0.6 mg/L SeNPs. Overall, these findings highlight SeNPs as a potential tool for the alleviation of La stress in plants, and also offer a favourable solution for environmental remediation and sustainable agriculture under La stress.

Molecular characterization and expression pattern of Rubisco activase gene GhRCAβ2 in upland cotton (Gossypium hirsutum L.)

BACKGROUND

Rubisco activase (RCA) is a pivotal enzyme that can catalyse the activation of Rubisco in carbon assimilation pathway. Many studies have shown that RCA may be a potential target for genetic manipulation aimed at enhancing photosynthetic efficiency and crop yield.

OBJECTIVE

To understand the biological function of the GhRCAβ2 gene in upland cotton, we cloned the coding sequence (CDS) of the GhRCAβ2 gene and investigated its sequence features, evolutionary relationship, subcellular localization, promoter sequence and expression pattern.

METHODS

The bioinformatics tools were used to analyze the sequence features of GhRCAβ2 protein. Transient transformation of Arabidopsis mesophyll protoplasts was performed to determine the subcellular localization of the GhRCAβ2 protein. The expression pattern of the GhRCAβ2 gene was examined by analyzing transcriptome data and using the quantitative real-time PCR (qRT-PCR).

RESULTS

The full-length CDS of GhRCAβ2 was 1317 bp, and it encoded a protein with a chloroplast transit peptide. The GhRCAβ2 had two conserved ATP-binding domains, and did not have the C-terminal extension (CTE) domain that was unique to the RCA α-isoform in plants. Evolutionarily, GhRCAβ2 was clustered in Group A, and had a close evolutionary relationship with the soybean RCA. Western blot analysis demonstrated that GhRCAβ2 was immunoreactive to the RCA antibody displaying a molecular weight similar to that of the RCA β-isoform. The GhRCAβ2 protein was found in chloroplast, aligning with its role as a vital enzyme in the process of photosynthesis. The GhRCAβ2 gene had a leaf tissue-specific expression pattern, and the yellow-green leaf mutant exhibited a decreased expression of GhRCAβ2 in comparison to the wild-type cotton plants. The GhRCAβ2 promoter contained several cis-acting elements that respond to light, phytohormones and stress, suggesting that the expression of GhRCAβ2 may be regulated by these factors. An additional examination of stress response indicated that GhRCAβ2 expression was influenced by cold, heat, salt, and drought stress. Notably, diverse expression pattern was observed across different stress conditions. Additionally, low phosphorus and low potassium stress may result in a notable reduction in the expression of GhRCAβ2 gene.

CONCLUSION

Our findings will establish a basis for further understanding the function of the GhRCAβ2 gene, as well as providing valuable genetic knowledge to improve cotton photosynthetic efficiency and yield under challenging environmental circumstances.

Integrated Analysis of Metabolome and Transcriptome Reveals Insights for Low Phosphorus Tolerance in Wheat Seedling

Low phosphorus (LP) stress leads to a significant reduction in wheat yield, primarily in the reduction of biomass, the number of tillers and spike grains, the delay in heading and flowering, and the inhibition of starch synthesis and grouting. However, the differences in regulatory pathway responses to low phosphorus stress among different wheat genotypes are still largely unknown. In this study, metabolome and transcriptome analyses of G28 (LP-tolerant) and L143 (LP-sensitive) wheat varieties after 72 h of normal phosphorus (CK) and LP stress were performed. A total of 181 and 163 differentially accumulated metabolites (DAMs) were detected for G28CK vs. G28LP and L143CK vs. L143LP, respectively. Notably, the expression of pilocarpine (C07474) in G28CK vs. G28LP was significantly downregulated 4.77-fold, while the expression of neochlorogenic acid (C17147) in L143CK vs. L143LP was significantly upregulated 2.34-fold. A total of 4023 differentially expressed genes (DEGs) were acquired between G28 and L143, of which 1120 DEGs were considered as the core DEGs of LP tolerance of wheat after LP treatment. The integration of metabolomics and transcriptomic data further revealed that the LP tolerance of wheat was closely related to 15 metabolites and 18 key genes in the sugar and amino acid metabolism pathway. The oxidative phosphorylation pathway was enriched to four ATPases, two cytochrome c reductase genes, and fumaric acid under LP treatment. Moreover, PHT1;1, TFs (ARFA, WRKY40, MYB4, MYB85), and IAA20 genes were related to the Pi starvation stress of wheat roots. Therefore, the differences in LP tolerance of different wheat varieties were related to energy metabolism, amino acid metabolism, phytohormones, and PHT proteins, and precisely regulated by the levels of various molecular pathways to adapt to Pi starvation stress. Taken together, this study may help to reveal the complex regulatory process of wheat adaptation to Pi starvation and provide new genetic clues for further study on improving plant Pi utilization efficiency.

Role of SiPHR1 in the Response to Low Phosphate in Foxtail Millet via Comparative Transcriptomic and Co-Expression Network Analyses

Enhancing the absorption and utilization of phosphorus by crops is an important aim for ensuring food security worldwide. However, the gene regulatory network underlying phosphorus use in foxtail millet remains unclear. In this study, the molecular mechanism underlying low-phosphorus (LP) responsiveness in foxtail millet was evaluated using a comparative transcriptome analysis. LP reduced the chlorophyll content in shoots, increased the anthocyanin content in roots, and up-regulated purple acid phosphatase and phytase activities as well as antioxidant systems (CAT, POD, and SOD). Finally, 13 differentially expressed genes related to LP response were identified and verified using transcriptomic data and qRT-PCR. Two gene co-expression network modules related to phosphorus responsiveness were positively correlated with POD, CAT, and PAPs. Of these, SiPHR1, functionally annotated as PHOSPHATE STARVATION RESPONSE 1, was identified as an MYB transcription factor related to phosphate responsiveness. SiPHR1 overexpression in Arabidopsis significantly modified the root architecture. LP stress caused cellular, physiological, and phenotypic changes in seedlings. SiPHR1 functioned as a positive regulator by activating downstream genes related to LP tolerance. These results improve our understanding of the molecular mechanism underlying responsiveness to LP stress, thereby laying a theoretical foundation for the genetic modification and breeding of new LP-tolerant foxtail millet varieties.

Sulfur supplementation enhances nitric oxide efficacy in reversal of chromium-inhibited Calvin cycle enzymes, photosynthetic activity, and carbohydrate metabolism in wheat

The present study demonstrated that exogenously-sourced nitric oxide (as SNP, sodium nitroprusside; NO donor) and sulfur (S) protected photosynthesis against chromium (Cr) stress in wheat (Triticum aestivum L. cv. HD 2851). Plants grown with 100 µM Cr exhibited higher reactive oxygen species (ROS) production, resulting in photosynthetic damage. The individual application of 50 µM NO increased carbohydrate metabolism as well as photosynthetic parameters, antioxidant system with higher transcriptional gene levels that encode the key enzymes for the Calvin cycle under Cr stress. These effects were more prominent when NO was applied with 1.0 mM SO₄^2-. An increase in the reduced glutathione (GSH) content obtained with NO was further enhanced by S and resulted in higher protection against Cr stress. The protective effect of NO with S against Cr toxicity on photosynthesis was reversed when buthionine sulfoximine (BSO; GSH biosynthetic inhibitor) was used. Application of BSO reversed the impact of NO plus S on photosynthesis under Cr stress, verifying that the ameliorating effect of NO was through S-assimilation and via GSH production. Thus, the availability of S to NO application can help reduce Cr toxicity and protect photosynthetic activity and expression of the Calvin cycle enzymes in leaves through the GSH involvement.

Phosphorus Availability Affects the Photosynthesis and Antioxidant System of Contrasting Low-P-Tolerant Cotton Genotypes

Phosphorus (P) is an essential macronutrient, and an important component of plant metabolism. However, little is known about the effects of low P availability on P absorption, the photosynthetic electron transport chain, and the antioxidant system in cotton. This study used cotton genotypes (sensitive FJA and DLNTDH and tolerant BX014 and LuYuan343) with contrasting low-P tolerance in a hydroponic experiment under 15 µM, 50 µM, and 500 μM P concentrations. The results showed that low P availability reduced plant development and leaf area, shoot length, and dry weight in FJA and DLNADH, compared to BX014 and LuYuan343. The low P availability decreased the gas-exchange parameters such as the net photosynthetic rate, transpiration rate, and stomatal conductance, and increased the intercellular CO₂ concentration. Chlorophyll a fluorescence demonstrated that the leaves' absorption and trapped-energy flux were largely steady. In contrast, considerable gains in absorption and trapped-energy flux per reaction center resulted from decreases in the electron transport per reaction center under low-P conditions. In addition, low P availability reduced the activities of antioxidant enzymes and increased the content of malondialdehyde in the cotton genotypes, especially in FJA and DLNTDH. Moreover, low P availability reduced the activity of PEPC and generated a decline in the content of ATP and NADPH. Our research can provide a theoretical physiological basis for the growth and tolerance of cotton under low-P conditions.

Physiological and Transcriptomic Analyses Uncover the Reason for the Inhibition of Photosynthesis by Phosphate Deficiency in Cucumis melo L

Phosphate (Pi) deficiency is a common phenomenon in agricultural production and limits plant growth. Recent work showed that long-term Pi deficiency caused the inhibition of photosynthesis and inefficient electron transport. However, the underlying mechanisms are still unknown. In this study, we used the physiological, histochemical, and transcriptomic methods to investigate the effect of low-Pi stress on photosynthetic gas exchange parameters, cell membrane lipid, chloroplast ultrastructure, and transcriptional regulation of key genes in melon seedlings. The results showed that Pi deficiency significantly downregulated the expression of aquaporin genes, induced an increase in ABA levels, and reduced the water content and free water content of melon leaves, which caused physiological drought in melon leaves. Therefore, gas exchange was disturbed. Pi deficiency also reduced the phospholipid contents in leaf cell membranes, caused the peroxidation of membrane lipids, and destroyed the ultrastructure of chloroplasts. The transcriptomic analysis showed that 822 differentially expressed genes (DEGs) were upregulated and 1254 downregulated by Pi deficiency in leaves. GO and KEGG enrichment analysis showed that DEGs significantly enriched in chloroplast thylakoid membrane composition (GO:0009535), photosynthesis-antenna proteins (map00196), and photosynthesis pathways (map00195) were downregulated by Pi deficiency. It indicated that Pi deficiency regulated photosynthesis-related genes at the transcriptional level, thereby affecting the histochemical properties and physiological functions, and consequently causing the reduced light assimilation ability and photosynthesis efficiency. It enriches the mechanism of photosynthesis inhibition by Pi deficiency.

Proteomic Analysis Dissects Molecular Mechanisms Underlying Plant Responses to Phosphorus Deficiency

Phosphorus (P) is an essential nutrient for plant growth. In recent decades, the application of phosphate (Pi) fertilizers has contributed to significant increases in crop yields all over the world. However, low efficiency of P utilization in crops leads to intensive application of Pi fertilizers, which consequently stimulates environmental pollution and exhaustion of P mineral resources. Therefore, in order to strengthen the sustainable development of agriculture, understandings of molecular mechanisms underlying P efficiency in plants are required to develop cultivars with high P utilization efficiency. Recently, a plant Pi-signaling network was established through forward and reverse genetic analysis, with the aid of the application of genomics, transcriptomics, proteomics, metabolomics, and ionomics. Among these, proteomics provides a powerful tool to investigate mechanisms underlying plant responses to Pi availability at the protein level. In this review, we summarize the recent progress of proteomic analysis in the identification of differential proteins that play roles in Pi acquisition, translocation, assimilation, and reutilization in plants. These findings could provide insights into molecular mechanisms underlying Pi acquisition and utilization efficiency, and offer new strategies in genetically engineering cultivars with high P utilization efficiency.

Differential responses of maize (Zea mays) at the physiological, biomolecular, and nutrient levels when cultivated in the presence of nano or bulk ZnO or CuO or Zn2+ or Cu2+ ions

Expanding applications of metal-based nanoparticles (NPs) in industry and agriculture have influenced agro-ecosystems. However, relatively little is known about the bioaccumulation, distribution, and phytotoxicity of ZnO-NPs, CuO-NPs, ZnO-bulk, CuO-bulk, Zn²⁺, or Cu²⁺ in maize. Plants were exposed to 0.05-2 mg ml^-1 or g^-1 of six tested materials in agar (7 days) in hydroponic medium (20 days), or sandy-clay-loam soil (20 or 40 days). Seed germination, emergence and lengths of plumules, principal and seminal roots were significantly inhibited by ZnO-NPs, CuO-NPs, Zn²⁺, and Cu²⁺. Toxicity was more pronounced in hydroponic culture than in soil, and perceptible alterations in biomolecules were evident. ICP-MS analysis exhibited progressive uptake of metals while morphological, elemental, and surface/deeper scanning showed translocation and distribution of NPs in tissues. Tested materials induced enhanced superoxide radical production, lipid peroxidation, and antioxidant enzymes and proline levels. Exposure significantly reduced P-accumulation, photosynthesis, and protein production. Zn²⁺ and Cu²⁺ were found to be more toxic than NPs. Compared to 20 days exposure in soil, toxicity slightly increased after 40 days. ZnO-NPs and CuO-NPs increased apoptotic sub-G1 population by 22.4% and 38%, respectively. These results provide a better understanding of the mechanistic aspects responsible for the nanotoxicities of ZnO- and CuO-NPs in maize.

Low pH alleviated salinity stress of ginger seedlings by enhancing photosynthesis, fluorescence, and mineral element contents

We investigated the effects of low pH on the photosynthesis, chlorophyll fluorescence, and mineral contents of the leaves of ginger plants under salt stress. This experiment involved four treatments: T1 (pH 6, 0 salinity), T2 (pH 4, 0 salinity), T3 (pH 6, 100 mmol L⁻¹ salinity) and T4 (pH 4, 100 mmol L⁻¹ salinity). This study showed that photosynthesis (Pn, Gs, WUE and Tr) and chlorophyll fluorescence (qP, Φ PSII, and Fv/Fm) significantly decreased under salt stress; however, all the parameters of the ginger plants under the low-pH treatment and salt stress recovered. Moreover, low pH reduced the content of Na and enhanced the contents of K, Mg, Fe and Zn in the leaves of ginger plants under salt stress. Taken together, these results suggest that low pH improves photosynthesis efficiency and nutrient acquisition and reduces the absorption of Na, which could enhance the salt tolerance of ginger.

Transcriptional, metabolic, physiological and developmental responses of switchgrass to phosphorus limitation

Knowing how switchgrass (Panicum virgatum L.) responds and adapts to phosphorus (P)-limitation will aid efforts to optimize P acquisition and use in this species for sustainable biomass production. This integrative study investigated the impacts of mild, moderate, and severe P-stress on genome transcription and whole-plant metabolism, physiology and development in switchgrass. P-limitation reduced overall plant growth, increased root/shoot ratio, increased root branching at moderate P-stress, and decreased root diameter with increased density and length of root hairs at severe P-stress. RNA-seq analysis revealed thousands of genes that were differentially expressed under moderate and severe P-stress in roots and/or shoots compared to P-replete plants, with many stress-induced genes involved in transcriptional and other forms of regulation, primary and secondary metabolism, transport, and other processes involved in P-acquisition and homeostasis. Amongst the latter were multiple miRNA399 genes and putative targets of these. Metabolite profiling showed that levels of most sugars and sugar alcohols decreased with increasing P stress, while organic and amino acids increased under mild and moderate P-stress in shoots and roots, although this trend reversed under severe P-stress, especially in shoots.

Low red/far-red ratio as a signal promotes carbon assimilation of soybean seedlings by increasing the photosynthetic capacity

BACKGROUND

Shading includes low light intensity and varying quality. However, a low red/far-red (R/Fr) ratio of light is a signal that affects plant growth in intercropping and close- planting systems. Thus, the low R/Fr ratio uncoupling from shading conditions was assessed to identify the effect of light quality on photosynthesis and CO2 assimilation. Soybean plants were grown in a growth chamber with natural solar radiation under four treatments, that is, normal (N, sunlight), N + Fr, Low (L) + Fr, and L light.

RESULTS

Low R/Fr ratio significantly increased the total biomass, leaf area, starch and sucrose contents, chlorophyll content, net photosynthetic rate, and quantum efficiency of the photosystem II compared with normal R/Fr ratio under the same light level (P < 0.05). Proteomic analysis of soybean leaves under different treatments was performed to quantify the changes in photosynthesis and CO2 assimilation in the chloroplast. Among the 7834 proteins quantified, 12 showed a > 1.3-fold change in abundance, of which 1 was related to porphyrin and chlorophyll metabolism, 2 were involved in photosystem I (PS I), 4 were associated with PS II, 3 proteins participated in photosynthetic electron transport, and 2 were involved in starch and sucrose metabolism. The dynamic change in these proteins indicates that photosynthesis and CO2 assimilation were maintained in the L treatment by up-regulating the component protein levels compared with those in N treatment. Although low R/Fr ratio increased the photosynthetic CO2 assimilation parameters, the differences in most protein expression levels in N + Fr and L + Fr treatments compared with those in N treatment were insignificant. Similar trends were found in gene expression through quantitative reverse transcription polymerase chain reaction excluding the gene expression of sucrose synthase possible because light environment is one of the factors affecting carbon assimilation.

CONCLUSIONS

Low R/Fr ratio (high Fr light) can increase the photosynthetic CO2 assimilation in the same light intensity by improving the photosynthetic efficiency of the photosystems.

PEATmoss (Physcomitrella Expression Atlas Tool): a unified gene expression atlas for the model plant Physcomitrella patens

Physcomitrella patens is a bryophyte model plant that is often used to study plant evolution and development. Its resources are of great importance for comparative genomics and evo-devo approaches. However, expression data from Physcomitrella patens were so far generated using different gene annotation versions and three different platforms: CombiMatrix and NimbleGen expression microarrays and RNA sequencing. The currently available P. patens expression data are distributed across three tools with different visualization methods to access the data. Here, we introduce an interactive expression atlas, Physcomitrella Expression Atlas Tool (PEATmoss), that unifies publicly available expression data for P. patens and provides multiple visualization methods to query the data in a single web-based tool. Moreover, PEATmoss includes 35 expression experiments not previously available in any other expression atlas. To facilitate gene expression queries across different gene annotation versions, and to access P. patens annotations and related resources, a lookup database and web tool linked to PEATmoss was implemented. PEATmoss can be accessed at https://peatmoss.online.uni-marburg.de.

Potential of calcium nitrate to mitigate the aluminum toxicity in Phaseolus vulgaris: effects on morphoanatomical traits, mineral nutrition and photosynthesis

Common bean (Phaseolus vulgaris) cultivation occurs mainly in regions with acidic soils, where high aluminum (Al) concentration is a major constraint to crop production. In this study, we evaluated tolerance and sensitivity traits to Al exposure and calcium (Ca) deficiency in bean plants, and determined the efficiency of Ca to mitigate the toxic Al effects. Two bean cultivars (BRS Estilo and Campos Gerais) were grown in three soil conditions: (I) soil liming with calcium hydroxide Ca(OH)₂ and Al unavailable (-Al+Ca); (II) fertilized soil with calcium nitrate [Ca(NO₃)₂·4H₂O] and Al available (+Al+Ca); and (III) soil without Ca addition and Al available (+Al-Ca). At the beginning of the reproductive stage, we evaluated the photosynthetic processes, mineral nutrition, and leaf anatomy and morphological traits of plants. The photosynthetic parameters were good tools for monitor Al sensitivity in bean. +Al+Ca soil treatment mitigated the deleterious effects of Al on growth and mineral nutrition of both bean cultivars. However, Ca did not prevent the toxic effects of Al on leaf anatomy. Al stress and Ca deficiency caused negative effects on nutrient content, photosynthetic activity and leaf anatomy of bean plants. Calcium mitigated Al toxicity, primarily in the Campos Gerais cultivar, showing the potential to improve bean crop productivity in acid soils.

Regulation of Ubiquitination Is Central to the Phosphate Starvation Response

As sessile organisms, plants have developed numerous strategies to overcome the limiting availability of the essential nutrient phosphate in nature. Recent studies reveal that post-translational modification (PTM) by ubiquitination is an important and central regulation mechanism in the plant phosphate starvation response (PSR). Ubiquitination precisely modulates the stability and trafficking of proteins in response to the heterogeneous phosphate supplement. Induction of autophagy provides novel insights into the molecular mechanisms under phosphate starvation. In this review, we present and discuss novel findings on the regulation of diverse PSRs through ubiquitination. Resolving these regulation mechanisms will pave the way to improve phosphate acquisition and utilization efficiency in crops.

Metabolomics reveals defensive mechanisms adapted by maize on exposure to high molecular weight polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons are an important group of persistent organic pollutants. Using plants to remediate PAHs has been recognized as a cost-effective and environmentally friendly technique. However, the overall impact of PAHs on the regulation of plant metabolism has not yet been explored. In this study, we analyzed the alteration in the maize (Zea mays L.) metabolome on exposure to high molecular weight PAHs such as benzo[a]pyrene (BaP) and pyrene (PYR) in a hydroponic medium, individually and as a mixture (BaP + PYR) using GC-MS. The differences in the metabolites were analyzed using XCMS (an acronym for various forms (X) of chromatography-mass spectrometry), an online-based data analysis tool. A significant variation in metabolites was observed between treatment groups and the unspiked control group. The univariate, multivariate and pathway impact analysis showed there were more significant alterations in metabolic profiles between individual PAHs and the mixture of BaP and PYR. The marked changes in the metabolites of galactose metabolism and aminoacyl tRNA biosynthesis in PAHs treated maize leaves exhibit the adaptive defensive mechanisms for individual and PAHs mixture. Therefore, the metabolomics approach is essential for an understanding of the complex biochemical responses of plants to PAHs contaminants. This knowledge will shed new light in the field of phytoremediation, bio-monitoring, and environmental risk assessment.

Physiological and Proteomics Analyses Reveal Low-Phosphorus Stress Affected the Regulation of Photosynthesis in Soybean

Previous studies have revealed a significant genetic relationship between phosphorus (P)-efficiency and photosynthesis-related traits in soybean. In this study, we used proteome profiling in combination with expression analysis, biochemical investigations, and leaf ultrastructural analysis to identify the underlying physiological and molecular responses. The expression analysis and ultrastructural analysis showed that the photosynthesis key genes were decreased at transcript levels and the leaf mesophyll and chloroplast were severely damaged after low-P stress. Approximately 55 protein spots showed changes under low-P condition by mass spectrometry, of which 17 were involved in various photosynthetic processes. Further analysis revealed the depression of photosynthesis caused by low-P stress mainly involves the regulation of leaf structure, adenosine triphosphate (ATP) synthesis, absorption and transportation of CO₂, photosynthetic electron transport, production of assimilatory power, and levels of enzymes related to the Calvin cycle. In summary, our findings indicated that the existence of a stringent relationship between P supply and the genomic control of photosynthesis in soybean. As an important strategy to protect soybean photosynthesis, P could maintain the stability of cell structure, up-regulate the enzymes’ activities, recover the process of photosystem II (PSII), and induce the expression of low-P responsive genes and proteins.

Source-sink interaction: a century old concept under the light of modern molecular systems biology

Many approaches to engineer source strength have been proposed to enhance crop yield potential. However, a well-co-ordinated source-sink relationship is required finally to realize the promised increase in crop yield potential in the farmer's field. Source-sink interaction has been intensively studied for decades, and a vast amount of knowledge about the interaction in different crops and under different environments has been accumulated. In this review, we first introduce the basic concepts of source, sink and their interactions, then summarize current understanding of how source and sink can be manipulated through both environmental control and genetic manipulations. We show that the source-sink interaction underlies the diverse responses of crops to the same perturbations and argue that development of a molecular systems model of source-sink interaction is required towards a rational manipulation of the source-sink relationship for increased yield. We finally discuss both bottom-up and top-down routes to develop such a model and emphasize that a community effort is needed for development of this model.