Comparative Transcriptomic Analysis Provides Novel Insights into the Blanched Stem of Oenanthe javanica

Abstract

In the agricultural field, blanching is a technique used to obtain tender, sweet, and delicious water dropwort stems by blocking sunlight. The physiological and nutritional parameters of blanched water dropwort have been previously investigated. However, the molecular mechanism of blanching remains unclear. In the present study, we investigated transcriptomic variations for different blanching periods in the stem of water dropwort (pre, mid, post-blanching, and control). The results showed that many genes in pathways, such as photosynthesis, carbon fixation, and phytohormone signal transduction as well as transcription factors (TFs) were significantly dysregulated. Blanched stems of water dropwort showed the higher number of downregulated genes in pathways, such as photosynthesis, antenna protein, carbon fixation in photosynthetic organisms, and porphyrin and chlorophyll metabolism, which ultimately affect the photosynthesis in water dropwort. The genes of hormone signal transduction pathways (ethylene, jasmonic acid, brassinosteroid, and indole-3-acetic acid) showed upregulation in the post-blanched water dropwort plants. Overall, a higher number of genes coding for TFs, such as ERF, BHLH, MYB, zinc-finger, bZIP, and WRKY were overexpressed in blanched samples in comparison with the control. These genes and pathways participate in inducing the length, developmental processes, pale color, and stress tolerance of the blanched stem. Overall, the genes responsive to blanching, which were identified in this study, provide an effective foundation for further studies on the molecular mechanisms of blanching and photosynthesis regulations in water dropwort and other species.

Influence of Blanching on the Gene Expression Profile of Phenylpropanoid, Flavonoid and Vitamin Biosynthesis, and Their Accumulation in Oenanthe javanica

“…We also reported that the higher antioxidant capacity of blanched water dropwort was due to the higher content of vitamins and soluble sugars [2]. Another study by reported that a significant number of the genes were found downregulated in photosynthesis-related pathways that eventually reduced the chlorophyll content in water dropwort due to blanching [10]. Our previous study also reported that blanched samples contained the upregulation of many genes in the plant hormone signal transduction pathways and transcription factors, such as ERF, bHLH, MYB, and zinc finger.…”

“…The RNA quality and quantity were determined with BioDrop uLite (80-3006-51). The cDNA library construction and transcriptomic sequencing were performed by Biomarker Technologies (Beijing, China) (http://www.biomarker.com.cn/, accessed on 4 February 2021) on the Illumina HiSeq 2000 platform [4,10,27].…”

“…The left files (read1 files) from all samples/libraries were assembled into a single big left.fq file and all files from the right (read2 files) were pooled into a single big right.fq file. The transcriptomic assembly was based on the left.fq and right.fq by using Trinity with min-kmer-cov fixed to 2 by default, and all other parameters were also set by default [4,10,27]. We submitted the transcriptomic data to the Sequence Read Archive (SRA) database of NCBI, and the SRA accession number is PRJNA722062.…”

“…Due to its particular aroma and flavor, it is used for garnishing different dishes and salads. The Chinese use the blanched stem of water dropwort with rice and other dishes in a fried or boiled form [2,7,10,11].…”

“…Our previous study also reported that blanched samples contained the upregulation of many genes in the plant hormone signal transduction pathways and transcription factors, such as ERF, bHLH, MYB, and zinc finger. We also highlighted the role of these pathways and genes in the stimulating length, development, and stress tolerance in the blanched stem of water dropwort [10]. However, the influence of blanching on the production of secondary metabolites and vitamins in the water dropwort has not been investigated at the transcriptomic level.…”