Comparative Transcriptome Analysis of Two Ipomoea aquatica Forsk. Cultivars Help to Explore Possible Mechanism of Cultivar-Dependent Accumulation of Cadmium

Tremendous differences in the capacity of Cd accumulation between low-Cd (QLQ) and high-Cd accumulation cultivar (T308) of water spinach (Ipomoea aquatica Forsk.) were observed in our previous study. Illumina high-throughput sequencing on root transcriptomes of well-characterized  two cultivars under transient (9 h) and long-term (72 h) Cd stresses were undertaken to characterize the specific Cd response of the two cultivars in the present study.

1. Based on de novotranscriptome assembly, total of 57524 unigenes were obtained in roots of water spinach. Among them, 6136 and 10064 unigenes were differential expressed in QLQ and T308, respectively.

2. Gene ontology (GO) analysis of all the differential expression genes (DEGs) between the two cultivars unravel significant difference in GO terms of cell wall, hormone metabolic process, cellular response to extracellular stimulus, response to extracellular stimulus.

3. Most of DEGs enriched pathways were consistent in two cultivars according to Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, indicating similar mechanism under Cd stress in water spinach. Glutathione metabolism pathway was significantly enriched only in T308. Most heavy metal transporters were higher expressed in T308 than in QLQ, while QLQ had higher expression of heavy metal detoxification related genes comparing to T308.

The observations will help to clarify molecular mechanisms associating to            Cd accumulation in water spinach and will be useful for speeding the breeding process of low-Cd cultivars based on molecular assistant breeding techniques.

Keywords: comparative transcriptome analysis, Ipomoea aquatica Forsk., low cadmium accumulation