Transcriptomic analysis of succulent stem development of Chinese kale ( var. Bailey) and its synthetic allotetraploid RNA sequencing.

Chinese kale ( var. Bailey, CC) is a succulent stem vegetable in the family. Its allotetraploid (AACC) vegetable germplasm, which was synthesized distant hybridization with the colloquially named 'yellow turnip' ( L. ssp. Matzg., AA), has a swelling stem similar to CC. To address the molecular mechanism of stem development for CC and AACC, RNA sequencing (RNA-seq) was used to investigate transcriptional regulation of their stem development at three key stages including 28 days, 42 days and the bolting stage (BS) after sowing. As a result, 32,642, 32,665, 33,816, 32,147, 32,293 and 32,275 genes were identified in six corresponding cDNA libraries. Among them, 25,459 genes were co-expressed, while 7,183, 7,206, 8,357, 6,688, 6,834 and 6,814 genes were specifically expressed. Additionally, a total of 29,222 differentially expressed genes (DEGs) were found for functional enrichment as well as many genes involved in plant hormones including gibberellin (GA), abscisic acid (ABA), cytokinin (CTK) and auxin (AUX). Based on gene expression consistency between CC and AACC, the gene families including and might be related to stem development. Among these, eight genes including , , , , , , and may play important roles in stem development based on their remarkable expression levels as confirmed by qRT-PCR. These findings provide a new theoretical basis for understanding the molecular mechanism of stem development in vegetable stem breeding.