Comparative transcriptome analysis of different heat stress responses between self-root grafting line and heterogeneous grafting line in rose

Rose is sensitive to high temperature which will make the rose go into a semi-dormancy state.Grafting is an excellent way to enhance rose heat tolerance.Here,heat-tolerant Rosa multiflora‘Huanong Wuci 1'(W)and heat-sensitive Rosa chinensis‘Old Blush’(X)were selected as experimental materials.The RNA-seq technique was used to investigate the transcriptomes of self-root grafting line(XX0),heterogeneous grafting line(XW0),self-root grafting line under 6 h heat stress(XX6),and heterogeneous grafting line under 6 h heat stress(XW6).Under high temperature stress,multiple signaling pathways were activated,moreover,a large number of transcription factors and functional genes were induced,especially the HSFs and HSPs with remarkably upregulated expression levels.The GO analysis showed that the differences in the expressions of the genes related to fatty acids and carbohydrates were observed between self-root grafting line and heterogeneous grafting line.In addition,14 P450s were differentially expressed,and one lectin gene was up-regulated in XW0 vs XW6,but down-regulated in XX0 vs XX6.Considering physiological and biochemical traits such as relative electrolyte leakage,SOD activity,proline,and total soluble sugars,DEGs involved in these processes may be key factors to resist high temperature.The present study provides an insight into the complex mechanism underlying grafting in response to heat stress.Our results indicate that grafting is an effective way to improve rose heat resistance.

The spatial pattern of grassland aboveground biomass on Xizang Plateau and its climatic controls

Aims Grassland is the most widely distributed vegetation type on the Xizang Plateau.Accurate remote sensing estimation of the grass-land aboveground biomass(AGB)in this region is influenced by the types of vegetation indexes(VIs)used,the grain size(resolution)of the remote sensing data and the targeted ecosystem features.This study attempts to answer the following questions:(i)Which VI can most accurately reflect the grassland AGB distribution on the Xizang Plateau?(ii)How does the grain size of remote sensing imagery affect AGB reflection?(iii)What is the spatial distribution pattern of the grassland AGB on the plateau and its relationship with the climate?Methods We investigated 90 sample sites and measured site-specific AGBs using the harvest method for three grassland types(alpine meadow,alpine steppe and desert steppe).For each sample site,four VIs,namely,Normalized Difference VI(NDVI),Enhanced VI,Normalized Difference Water Index(NDWI)and Modified Soil-Adjusted VI(MSAVI)were extracted from the Moderate Resolution Imaging Spectroradiometer(MODIS)products with grain sizes of 250 m and 1 km.Linear regression models were employed to iden-tify the best estimator of the AGB for the entire grassland and the three individual grassland types.Paired Wilcoxon tests were applied to assess the grain size effect on the AGB estimation.General linear models were used to quantify the relationships between the spatial distribution of the grassland AGB and climatic factors.Important Findings The results showed that the best estimator for the entire grass-land AGB on the Xizang Plateau was MSAVI at a 250 m grain size(MSAVI_(250 m)).For each individual grassland type,the best estimator was MSAVI at a grain size of 250 m for alpine meadow,NDWI at a grain size of 1 km for alpine steppe and NDVI at a grain size of 1 km for desert steppe.The explanation ability of each VI for the grassland AGB did not significantly differ for the two grain sizes.Based on the best fit model(AGB=−10.80+139.13 MSAVI_(250 m)),the spatial pattern of the grassland AGB on the plateau was characterized.The AGB varied from 1 to 136 g m^(−2).Approximately 59%of total spatial variation in the AGB for the entire grassland was explained by the combination of the mean annual precipitation(MAP)and mean annual temperature.The explanatory power of MAP was weaker for each individual grassland type than that for the entire grassland.This study illustrated the high efficiency of the VIs derived from MODIS data in the grassland AGB estimation on the Xizang Plateau due to the vegetation homogeneity within a 1×1 km pixel in this region.Furthermore,MAP is a primary driver on the spatial variation of AGB at a regional scale.