Chengyun Li

Crop diversity for yield increase.

Traditional farming practices suggest that cultivation of a mixture of crop species in the same field through temporal and spatial management may be advantageous in boosting yields and preventing disease, but evidence from large-scale field testing is limited. Increasing crop diversity through intercropping addresses the problem of increasing land utilization and crop productivity. In collaboration with farmers and extension personnel, we tested intercropping of tobacco, maize, sugarcane, potato, wheat and broad bean – either by relay cropping or by mixing crop species based on differences in their heights, and practiced these patterns on 15,302 hectares in ten counties in Yunnan Province, China. The results of observation plots within these areas showed that some combinations increased crop yields for the same season between 33.2 and 84.7% and reached a land equivalent ratio (LER) of between 1.31 and 1.84. This approach can be easily applied in developing countries, which is crucial in face of dwindling arable land and increasing food demand.

Plant-Plant-Microbe Mechanisms Involved in Soil-Borne Disease Suppression on a Maize and Pepper Intercropping System

Background Intercropping systems could increase crop diversity and avoid vulnerability to biotic stresses. Most studies have shown that intercropping can provide relief to crops against wind-dispersed pathogens. However, there was limited data on how the practice of intercropping help crops against soil-borne Phytophthora disease. Principal Findings Compared to pepper monoculture, a large scale intercropping study of maize grown between pepper rows reduced disease levels of the soil-borne pepper Phytophthora blight. These reduced disease levels of Phytophthora in the intercropping system were correlated with the ability of maize plants to form a “root wall” that restricted the movement of Phytophthora capsici across rows. Experimentally, it was found that maize roots attracted the zoospores of P. capsici and then inhibited their growth. When maize plants were grown in close proximity to each other, the roots produced and secreted larger quantities of 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (DIMBOA) and 6-methoxy-2-benzoxazolinone (MBOA). Furthermore, MBOA, benzothiazole (BZO), and 2-(methylthio)-benzothiazole (MBZO) were identified in root exudates of maize and showed antimicrobial activity against P. capsici. Conclusions Maize could form a “root wall” to restrict the spread of P. capsici across rows in maize and pepper intercropping systems. Antimicrobe compounds secreted by maize root were one of the factors that resulted in the inhibition of P. capsici. These results provide new insights into plant-plant-microbe mechanisms involved in intercropping systems.

Endoplasmic reticulum protein 29 protects cortical neurons from apoptosis and promoting corticospinal tract regeneration to improve neural behavior via caspase and Erk signal in rats with spinal cord transection.

Following spinal cord injury (SCI), limit spontaneous functional recovery often emerged. However, the neuronal mechanisms associated with this phenomenon still remains obscure. By using proteomics analysis, endoplasmic reticulum protein 29 (ERp29) was discovered to increase in the motor cortexes of spinal cord transection (SCT) rats for 28 days post-operation (dpo) compared with in 14dpo. Then, the change in the expression of ERp29 was confirmed by using reverse transcription polymerase chain reaction (RT-PCR) and Western blot. To determine the role of ERp29 in the recovery of locomotor functions following SCT, lentiviral vectors were used to up- and downregulate the expression level of ERp29. Here, we found that cortical neurons in vitro with high level of ERp29 expression exhibited a significant proliferation, characterized by smaller size of soma and more extensive axon outgrowth, compared with neurons used as control, while ERp29 silence got the opposite results. In vivo, Lentivirus was inject into the cerebral cortex following SCT at thoracic level 10, which resulted in an increase number of neuronal nuclei(NeuN)-positive cells and less apoptotic cells. Moreover, increased PKC-γ immunoreactivity density was also found in the spinal cord T9 level compared with control rats. This was associated with a great functional improvement, indicated by Basso, Beattie, Bresnahan (BBB) locomotor rating scale. Lastly, we verified that ERp29 acts as a regulator by regulating a group of genes related with cell survival and apoptosis, involving in caspase and Erk, but not PI3K. Our findings showed that ERp29 can improve locomotor function by promoting neuronal survival and axonal regeneration in SCT rats via caspase and Erk signal pathway.

Proteomics insights into the basis of interspecific facilitation for maize (Zea mays) in faba bean (Vicia faba)/maize intercropping

UNLABELLED Faba bean/maize intercropping significantly promotes maize productivity in phosphorus-deficient soils. This has been attributed to the below-ground interactions including rhizosphere effects and spatial effects. Nevertheless, the molecular mechanisms underlying these interactions have been scarcely investigated. Here, three types of pots were used to distinguish the influences of rhizosphere effects vs. spatial effects. Phosphorus and nitrogen uptake of shoots, biomass, total root length, and root classification were evaluated between the three treatments. Quantitative RT-PCR and proteomics analyses were conducted to investigate the putative components in the molecular basis of these interactions. Quantitative RT-PCR results indicated that rhizosphere effects promoted maize phosphorus status at molecular levels. 66 differentially accumulated protein spots were successfully identified through proteomics analyses. Most of the protein species were found to be involved in phosphorus, nitrogen, and allelochemical metabolism, signal transduction, or stress resistance. The results suggest that rhizosphere effects promoted phosphorus and nitrogen assimilation in maize roots and thus enhanced maize growth and nutrient uptake. The reprogramming of proteome profiles suggests that rhizosphere effects can also enhance maize tolerance through regulating the metabolism of allelochemicals and eliciting systemic acquired resistance via the stimulation of a mitogen-activated protein kinase signal pathway. BIOLOGICAL SIGNIFICANCE The results obtained contribute to a comprehensive understanding of the response of maize to the changes of rhizosphere condition influenced by the below-ground interactions in faba bean/maize intercropping at molecular levels. The identified protein species involved in nutrient metabolisms and stress resistance reveal the molecular basis underlying the major advantages of effective nutrient utilization and higher stress tolerance in legume/cereal intercropping systems. This work provides essential new insights into the putative components in the molecular basis of interspecific facilitation for maize in faba bean/maize intercropping.

Upregulation of eIF-5A1 in the paralyzed muscle after spinal cord transection associates with spontaneous hindlimb locomotor recovery in rats by upregulation of the ErbB, MAPK and neurotrophin signal pathways.

It is well known that trauma is frequently accompanied by spontaneous functional recovery after spinal cord injury (SCI), but the underlying mechanisms remain elusive. In this study, BBB scores showed a gradual return of locomotor functions after SCT. Proteomics analysis revealed 16 differential protein spots in the gastrocnemius muscle between SCT and normal rats. Of these differential proteins, eukaryotic translation initiation factor 5A1 (elf-5A1), a highly conserved molecule throughout eukaryotes, exhibited marked upregulation in the gastrocnemius muscle after SCT. To study the role of eIF-5A1 in the restoration of hindlimb locomotor functions following SCT, we used siRNA to downregulate the mRNA level of eIF-5A1. Compared with untreated SCT control rats, those subjected to eIF-5A1 knockdown exhibited impaired functional recovery. Moreover, gene expression microarrays and bioinformatic analysis showed high correlation between three main signal pathways (ErbB, MAPK and neurotrophin signal pathways) and eIF-5A1. These signal pathways regulate cell proliferation, differentiation and neurocyte growth. Consequently, eIF-5A1 played a pivotal role via these signal pathways in hindlimb locomotor functional recovery after SCT, which could pave the way for the development of a new strategy for the treatment of spinal cord injury in clinical trials.

Extended expression of B-class MADS-box genes in the paleoherb Asarum caudigerum

Asarum caudigerum (Aristolochiaceae) is a paleoherb species that is important for research in origin and evolution of angiosperm flowers due to its basal position in the angiosperm phylogeny. In this study, a subtracted floral cDNA library from floral buds of A. caudigerum was constructed and cDNA arrays by suppression subtractive hybridization were generated. cDNAs of floral buds at different stages before flower opening and of leaves at the seedling stage were used. The macroarray analyses of expression profiles of isolated floral genes showed that 157 genes out of the 612 unique ESTs tested revealed higher transcript abundance in the floral buds and uppermost leaves. Among them, 78 genes were determined to be differentially expressed in the perianth, 62 in the stamens, and 100 genes in the carpels. Quantitative real-time PCR of selected genes validated the macroarray results. Remarkably, APETALA3 (AP3) B-class genes isolated from A. caudigerum were upregulated in the perianth, stamens and carpels, implying that the expression domain of B-class genes in this basal angiosperm was broader than those in their eudicot counterparts.

Structure and evolution of full-length LTR retrotransposons in rice genome

The long terminal repeat (LTR) retrotransposons are the most abundant class of transposable elements in plant genomes and play important roles in genome divergence and evolution. Their accumulation is the main factor influencing genome size increase in plants. Rice (Oryza sativa L.) is a model monocot and is the focus of much biological research due to its economic importance. We conducted a comprehensive survey of full-length LTR retrotransposons based on the completed genome of japonica rice variety Nipponbare (TIGR Release 5), with the newly published tool LTR-FINDER. The elements could be categorized into 29 structural domain categories (SDCs), and their total copy number identified was estimated at >6,000. Most of them were relatively young: more than 90% were less than 10 My. There existed a high level of activity among them as a whole at 0–1 Mya, but different categories possessed distinct amplification patterns. Most recently inserted elements were specific to the rice genome, while a few were conserved across species. This study provides new insights into the structure and evolutionary history of the full-length retroelements in the rice genome.

Priming maize resistance by its neighbors: activating 1,4-benzoxazine-3-ones synthesis and defense gene expression to alleviate leaf disease

Plant disease can be effectively suppressed in intercropping systems. Our previous study demonstrated that neighboring maize plants can restrict the spread of soil-borne pathogens of pepper plants by secreting defense compounds into the soil. However, whether maize plant can receive benefits from its neighboring pepper plants in an intercropping system is little attention. We examined the effects of maize roots treated with elicitors from the pepper pathogen Phytophthora capsici and pepper root exudates on the synthesis of 1,4-benzoxazine-3-ones (BXs), the expression of defense-related genes in maize, and their ability to alleviate the severity of southern corn leaf blight (SCLB) caused by Bipolaris maydis. We found that SCLB was significantly reduced after the above treatments. The contents of 1,4-benzoxazine-3-ones (BXs: DIBOA, DIMBOA, and MBOA) and the expression levels of BX synthesis and defense genes in maize roots and shoots were up-regulated. DIMBOA and MBOA effectively inhibited the mycelium growth of Bipolaris maydis at physiological concentrations in maize shoots. Further studies suggested that the defense related pathways or genes in maize roots and shoots were activated by elicitors from the P. capsici or pepper root exudates. In conclusion, maize increased the levels of BXs and defense gene expression both in roots and shoots after being triggered by root exudates and pathogen from neighboring pepper plants, eventually enhancing its resistance.

Proteomic Analysis of the Relationship between Metabolism and Nonhost Resistance in Soybean Exposed to Bipolaris maydis.

Nonhost resistance (NHR) pertains to the most common form of plant resistance against pathogenic microorganisms of other species. Bipolaris maydis is a non-adapted pathogen affecting soybeans, particularly of maize/soybean intercropping systems. However, no experimental evidence has described the immune response of soybeans against B. maydis. To elucidate the molecular mechanism underlying NHR in soybeans, proteomics analysis based on two-dimensional polyacrylamide gel electrophoresis (2-DE) was performed to identify proteins involved in the soybean response to B. maydis. The spread of B. maydis spores across soybean leaves induced NHR throughout the plant, which mobilized almost all organelles and various metabolic processes in response to B. maydis. Some enzymes, including ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), mitochondrial processing peptidase (MPP), oxygen evolving enhancer (OEE), and nucleoside diphosphate kinase (NDKs), were found to be related to NHR in soybeans. These enzymes have been identified in previous studies, and STRING analysis showed that most of the protein functions related to major metabolic processes were induced as a response to B. maydis, which suggested an array of complex interactions between soybeans and B. maydis. These findings suggest a systematic NHR against non-adapted pathogens in soybeans. This response was characterized by an overlap between metabolic processes and response to stimulus. Several metabolic processes provide the soybean with innate immunity to the non-adapted pathogen, B. maydis. This research investigation on NHR in soybeans may foster a better understanding of plant innate immunity, as well as the interactions between plant and non-adapted pathogens in intercropping systems.

Developmental Genetics of the Perianthless Flowers and Bracts of a Paleoherb Species, Saururus chinensis

Saururus chinensis is a core member of Saururaceae, a perianthless (lacking petals or sepals) family. Due to its basal phylogenetic position and unusual floral composition, study of this plant family is important for understanding the origin and evolution of perianthless flowers and petaloid bracts among angiosperm species. To isolate genes involved in S. chinensis flower development, subtracted floral cDNA libraries were constructed by using suppression subtractive hybridization (SSH) on transcripts isolated from developing inflorescences and seedling leaves. The subtracted cDNA libraries contained a total of 1,141 ESTs and were used to create cDNA microarrays to analyze transcript profiles of developing inflorescence tissues. Subsequently, qRT-PCR analyses of eight MADS-box transcription factors and in situ hybridizations of two B-class MADS-box transcription factors were performed to verify and extend the cDNA microarray results. Finally, putative phylogenetic relationships within the B-class MADS-box gene family were determined using the discovered S. chinensis B-class genes to compare K-domain sequences with B genes from other basal angiosperms. Two hundred seventy-seven of the 1,141 genes were found to be expressed differentially between S. chinensis inflorescence tissues and seedling leaves, 176 of which were grouped into at least one functional category, including transcription (14.75%), energy (12.59%), metabolism (9.12%), protein-related function (8.99%), and cellular transport (5.76%). qRT-PCR and in situ hybridization of selected MADS-box genes supported our microarray data. Phylogenetic analysis indicated that a total of six B-class MADS-box genes were isolated from S. chinensis. The differential regulation of S. chinensis B-class MADS-box transcription factors likely plays a role during the development of subtending bracts and perianthless flowers. This study contributes to our understanding of inflorescence development in Saururus, and represents an initial step toward understanding the formation of petaloid bracts in this species.