Abstract:

In order to reveal the difference between thick root (TR) and storage root (SR) of sweetpotato with difference drought tolerance from transcriptional level, and further explicit the mechanism of roots differentiation and drought tolerance by simulating field drought in dry shed with artificial water control, two varieties including ‘Jishu21’ (‘JS21’ ) with strong drought tolerance and ‘Jizishu1’ (‘JZ1’) with weak drought tolerance were chosen as research materials. Transcriptome analysis of sweet potato thick root and storage root was carried out. The results indicated GO classification of differentially expressed genes (DEGs) of the two varieties was similar to that of KEGG enrichment. Under drought stress, 84 DEGs between SR and TR of ‘JS21’ mainly enriched the accumulation of starch and sucrose metabolic pathway, while 112 DEGs between SR and TR of ‘JZ1’ mainly enriched ribosomal metabolic pathway. Among different varieties, 224 DEGs between ‘JS21’ and ‘JZ1’ were found in SR, but 204 DEGs between ‘JS21’ and ‘JZ1’ were counted in TR, and all mainly enriched ribosomal metabolic pathway. Further analysis by transcription factors and hormones metabolism showed that ARF-like transcription factors in storage root and NAC-like transcription factors in thick root of ‘JS21’ were more differentially expressed than ‘JZ1’ under drought stress. The expression of genes involved in carotenoid biosynthesis pathway was up-regulated, while genes involved in brassinosteroid biosynthesis pathway were down-regulated in both thick root and storage root of ‘JS21’. In the same variety, the gene expression of α-linolenic acid metabolic pathway in ‘JS21’ storage root was up-regulated compared with thick root. In conclusion, sweetpotato with strong drought tolerance can maintain starch and sucrose metabolism under drought conditions by coordinating the expression of drought tolerance genes and growth-related transcription factors, balancing drought tolerance hormones (ABA, JA) and growth related hormones (IAA, BR), so as to improve the drought resistance and ensure the formation of yield.

Key words: sweetpotato, drought, roots, transcriptome, brassinosteroid, transcription factors