| Poplar is a generic term for deciduous trees of the genus Populus of the Salicaceae family.As one of the main afforestation tree species in the north,it has the characteristics of strong adaptability,rapid growth and easy reproduction.It is ideal for various types of shelter forests and wood production species.However,the maturation effect in the process of asexual reproduction of poplars will have a serious impact on clonal afforestation.In adult poplar plants,different parts of the tissues have different degrees of physiological aging,which will produce obvious maturation effects during asexual reproduction.At the same time,there are two types of leaves in adult poplar plants,namely,long-branched leaves growing on current-year branches and short branch leaves growing on non-current-year branches.There are significant differences in their morphological growth.In this study,the adult trees of Populus glandularis were studied,and the morphological and physiological differences of long branches and short branches in different parts and the same part were measured.Based on transcriptome sequencing technology,the differences in gene expression of different parts and different types of leaves were explored.The maturation effect of Populus glandularis provides reference.The main findings are as follows:(1)There is no obvious difference in leaf morphology in different parts.The leaf morphology of long branch leaves and short branch leaves are significant different.The Leaf area,Leaf perimeter,Leaf length,Leaf width and Number indents of long branch leaves are significantly larger than short branch leaves.The anatomical structure of leaves in different parts has no obvious regular changes,and the anatomical structures of different types of leaves are significantly different.The Thickness of palisade tissue and CTR values of long branch leaves are significantly larger than short branch leaves.(2)The contents of photosynthetic pigments in different parts of the leaves are significantly different.The chlorophyll a and total chlorophyll content of the lower leaves are significantly greater than those of the upper and middle parts.The content of chlorophyll a is 1.83 and 1.28 times that of the upper and middle parts,respectively,and the total chlorophyll content is 1.13 of the upper and middle parts respectively.And 1.19 times.There is no obvious difference in light and pigment content between long branch leaves and short branch leaves.In terms of antioxidant enzyme system,there are obvious changes between different parts of the leaves.The SOD enzyme activity of the lower leaves is significantly higher than that of the upper and middle parts,and the MDA content appears as middle part> upper part> lower part.There is no obvious difference in antioxidant enzyme system between long branch leaves and short branch leaves.(3)There are significant differences in the nutrient content between different parts of the leaves.The starch content of the lower leaves is significantly lower than that of the upper and middle parts,which are 29% and 22% lower than the upper and middle parts,respectively.The nutrient content of long branch leaves and short branch leaves did not change significantly.The IAA content of different parts of the leaves showed a rising trend with the decrease in height,and the ABA content of different parts of the leaves showed a changing trend of middle>upper>lower.There is a significant difference in hormone content between long branch leaves and short branch leaves.The IAA and IAA/ABA of long-branched leaves were significantly higher than those of short-branched leaves,and the ZR content showed the opposite trend of change.Through transcriptome analysis,the higher IAA content in leaves may be related to the relative number of up-regulated and down-regulated genes in the auxin signal transduction pathway.(4)Transcriptome sequencing obtained 79.3Gb of data,and the average amount of data per sample was 6.6Gb.The difference genes were screened.The SC-VS-SD,XC-VS-XD,SC-VS-XC and SD-VS-XD comparison groups were screened to 8744,9326,208 and 524 significantly different genes,respectively.The number of different genes between different parts of leaves is less than the number of different genes between different types of leaves.(5)The GO and KEGG enrichment analysis of the significantly different genes in each comparison group found that the SC-VS-XC and SD-VS-XD comparison groups were all enriched in plant hormone signal transduction,photosynthesis,starch and sucrose metabolism pathways.It is speculated that the formation of the difference between the upper and lower blades is related to these passages.The pathways enriched in the SC-VS-SD and XC-VS-XD comparison groups are very similar,mainly including plant hormone signal transduction,phenylpropane biosynthesis and amino acid biosynthesis.(6)A total of 32 shared differentially expressed genes were found in the SC-VS-XC and SD-VS-XD comparison groups.The KEGG enrichment analysis of the shared differentially expressed genes found that the differential genes were significantly enriched in the photosynthesis pathway,and the enrichment to the Gene annotation was performed on the two genes in the pathway,and it was found that both genes encode Psb R protein,and the gene expression in the lower leaves was up-regulated.KEGG pathway analysis was performed on the common differential genes of the different types of leaf comparison groups,and it was found that the pathways enriched in the two comparison groups were very similar.The auxin signal transduction process was analyzed and it was found that the gene expression in the short branches and leaves were all down-regulated. |
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