Exogenous SA Initiated Defense Response and Multi-signaling Pathway in Tetraploid Potato SD20

Salicylic acid(SA) is an important signaling substance that plays an important role in plant growth, development and disease resistance.In order to further understand the role of the SA pathway in potato disease resistance and identify SA signaling key genes, gene expression profiling of the late blight resistance genotype SD20 was performed under exogenous SA application. A total of 28 572 unigenes were assembled,of which 4 564 were differentially expressed. Analysis of differentially expressed genes(DEGs) showed that multiple signaling pathways such as SA, jasmonic acid, ethylene, abscisic acid, auxin, and brassinolide were involved in response to exogenous SA. Many plant defense signalrelated genes involved in protein serine/threonine kinase activity and plant-pathogen interaction, were significantly enriched. These were consistent with the interaction results of SD20 and Phytophthora infestans in our previous study, indicating that exogenous SA stimulated the resistance response and initiated a similar defense pathway compared to pathogen infection in SD20, which confirmed crosstalk of the SA signaling pathway with a pathogen-induced disease resistance signal pathway in plant. Moreover, transcriptome analysis revealed that ROS1 was positively regulated by SA in potato for the first time. SA-induced gene expression profiling provides insight into SA signaling and its mechanisms in disease defense systems.

Effects of Powder Ridge Cultivation on Growth and Yield of Hunan Cassava

[Objective] The aim was to explore a suitable cultivation approach for cassava in Hunan province. [Method] With SC9(Southern China 9) as test materials, the test included four treatment methods, as follows: control group by traditional cultivation with crops uncovered(CK), treatment 1 by traditional cultivation with mulch coverage, treatment 2 by powder ridge cultivation with crops uncovered, and treatment 3 by powder ridge cultivation with mulch coverage. Water and fertilizer managements were kept the same. [Result] Compared with traditional cultivation(CK), the treatment by powder ridge cultivation with mulch coverage performed better. Specifically, yield per unit area reached 44 790 kg/hm2, increasing by 86.38%(20 760 kg/hm2) than that of control; starch content grew by 17.24%. The cultivation method considerably improved cassava yield and quality. [Conclusion] Powder ridge cultivation with mulch coverage is a cultivation approach suitable for cassava in Hunan province.

Exogenously applied methyl Jasmonate induces early defense related genes in response to Phytophthora infestans infection in potato plants

In order to elucidate the contributions of JA in orchestrating disease resistance in potato plants,the potato genotype‘SD20’,which exhibits strong resistance against the highly virulent Phytophthora infestans isolate CN152,while infected by the super virulent isolate 2013-18-306,was treated with exogenous JA and then challenged by inoculation with 2013-18-306.The results showed that exogenously applied JA significantly delayed the onset and alleviated the symptoms of late blight,indicating exogenous JA could induce resistance to P.infestans in the early biotrophic stage of infection in‘SD20’plants.To further clarify the role of JA in the early defense response and identify key genes involved in JA signal transduction,gene expression profiling via RNA sequencing(RNA-seq)in‘SD20’plants treated with exogenously applied JA was performed.A total of 2927 differentially expressed genes were specifically induced,the majority encoded transcription factors,protein kinases,secondary metabolites,defense enzymes and disease resistance related proteins.GO functional annotation and KEGG metabolic pathway analysis showed that exogenously applied JA rapidly induced the expression of genes related to immune response regulation,pathogen defense,and other biological processes,and stimulated endogenous JA synthesis and signal transduction,and the overall early pathogen defense response in‘SD20’.These results provide useful information in understanding the JA’s function involved in pathogen defense responses and a theoretical basis for the application of JA in potato production.

Relationship Between Net Photosynthetic Rate of Cassava SC205 and Its Physio-ecological Factors

[Objective] The aim was to measure photosynthetic characters of SC 205, a cassava cultivar, and explore the relationships of the net photosynthetic rate(Pn) with physiological and ecological factors. [Method] The diurnal variations of photosynthesis in leaves of SC205 were studied by LICOR-6400 portable photosynthesis system, and the relationships of the net photosynthetic rate(Pn) with physiological and ecological factors were studied by simple correlation analysis and path analysis. [Result] The curve of diurnal variation of Pn showed single peak at 10:00 am at 24.07 μ mol CO2m2/s, without showing midday depression; the diurnal changes of stomatal conductance(Gs), transpiration rate(Tr), leaf temperature(Tl), air temperature(Ta) and photosynthetic active radiation(PAR) all showed single peak curves, and there were positive relationships of Pn with Gs, Tr, Tl, Ta and PAR. The diurnal variations of intercellular CO2concentration(Ci), atmospheric CO2concentration(Ca), relative humidity(RH) showed in a U-shape curve. There were highly significant positive correlation of Pn with Gs and PAR; the diurnal variation of Pn had highly significant negative correlations with Ci and Ca. The direct impact of physiological factors on Pn was as follows: Ci>Gs>Tl>Tr, and the direct impact of ecological factors was RH >PAR >Ca >Ta. [Conclusion] The research showed that Ci, Gs and Tr play very important roles in the changes of Pn among the physiological factors, and PAR and Ca affect the changes of Pn among the ecological factors.

Spatial Pattern Change Simulation of Land Use in Yongchuan District of Chongqing City

In order to study the county scale land use structure during the rapid urbanization and more accurately grasp the dynamic process of land use and cover change,we combine GIS technology with CLUE-S model to research the spatial pattern change of land use in Yongchuan District of Chongqing City. The results show that the forest and farmland were main land use types going through changes in Yongchuan District during 2000-2010,accounting for more than 90% of the total area in each year; during 2000- 2010,the urban area was significantly increased,an increase of 16. 11%,and the urban area during 2005- 2010 was changed more dramatically than during 2000- 2005; forest area was slightly increased and farmland area was reduced by 1660 ha in 10 years. We set three scenarios on land use change in Yongchuan District for simulation and compare the predicted results. It can be concluded that driven by rapid urbanization,the change in land use landscape pattern in Yongchuan District is mainly focused on forest and farmland,the urban area is substantially increased,and the forest area also shows an increasing trend while the farmland area is reduced accordingly. Under ecological protection scenarios,the land use type having a protective effect on the ecological environment achieves better control effect.

Chloroplast DNA reveals genetic population structure in Sinomenium acutum in subtropical China

Objective:The population density and diversity of Sinomenium acutum(Menispermaceae)have been greatly reduced recently by overharvesting for medicinal purposes in China.Therefore,it is urgent that the remaining populations are investigated,and that strategies for the utilization and conservation of this species are developed.This study aimed to find the possible glacial refugia and define the genetic diversity of S.acutum for its proper utilization and conservation.Methods:A total of 77 S.acutum samples were collected from four locations,Qinling Mountains,Daba Mountains,Dalou Mountains,and Xuefeng Mountains,in subtropical China.Genetic diversity among and between these populations were phylogenetically analyzed using four chloroplast DNA molecular markers(atpI-atpH,trnQ-50 rps16,trnH-psbA and trnL-trnF).Results:A total of 14 haplotypes(C1 to C14)were found in collected samples.Haplotypes C1 and C3 were shared among all populations,with C3 as the ancestral haplotype.Haplotypes C11 and C12 diverged the most from C3 and other haplotypes.No obvious phylogeographic structure was found in four locations using the GST/NST test.There is no evidence of rapid demographic expansion in S.acutum based on the mismatch distribution,and the results of Tajima’s D test,and Fu’s FS test.Our analyses of molecular variance revealed a high level of genetic variation within populations.In contrast,the genetic differentiation among S.acutum populations was low,indicating frequent gene flow.Conclusion:Xuefeng,Dalou,and Daba Mountains were possible glacial refugia for the populations of S.acutum.C1,C3,C11 and C12 haplotypes of S.acutum should be carefully preserved and managed for their genetic value.

The Genome of Medicinal Plant Macleaya cordata Provides New Insights into Benzylisoquinoline Alkaloids Metabolism

The overuse of antibiotics in animal agriculture and medicine has caused a series of potential threats to public health. Macleaya cordata is a medicinal plant species from the Papaveraceae family, providing a safe resource for the manufacture of antimicrobial feed additive for livestock. The active constituents from M. cordata are known to include benzylisoquinoline alkaloids （BIAs） such as sanguinarine （SAN） and chelerythrine （CHE）, but their metabolic pathways have yet to be studied in this non-model plant. The active biosynthesis of SAN and CHE in M. cordata was first examined and confirmed by feeding ^13C-labeled tyrosine. To gain further insights, we de novo sequenced the whole genome of M. cordata, the first to be sequenced from the Papaveraceae family. The M. cordata genome covering 378 Mb encodes 22,328 predicted protein-coding genes with 43.5% being transposable elements. As a member of basal eudicot, M. cordata genome lacks the paleohexaploidy event that occurred in almost all eudicots. From the genomics data, a complete set of 16 metabolic genes for SAN and CHE biosynthesis was retrieved, and 14 of their biochemical activities were validated. These genomics and metabolic data show the conserved BIA metabolic pathways in M. cordata and provide the knowledge foundation for future productions of SAN and CHE by crop improvement or microbial pathway reconstruction.