Transcriptome differential display of a drought‐tolerant early flowering spineless mutant of safflower (Carthamus tinctorius) and identification of candidate genes

Abstract

AbstractOne of the best candidates to face the increasing environmental stresses is safflower (Carthamus tinctorius L.) with natural tolerance to multiple abiotic stresses including drought. In the present study, transcriptome profile of a spineless drought‐tolerant mutant of safflower with early flowering was compared to its spiny wild type. In differential RNA‐Seq analyses more than 400 differentially expressed genes (DEGs) were identified in spineless drought‐tolerant mutant. The expression of 8 top DEGs, mostly related to the contrasting traits, was confirmed by real‐time quantitative reverse transcription PCR. Transcription factors (TFs) followed by protein kinases had the highest frequency among the identified DEGs. TF families involved in the regulation of cell cycle, development, and environmental responses were prevalent in DEGs of spineless drought‐tolerant mutant, including NAC, bHLH, MYB, HD‐ZIP, and ERF. Three Kyoto Encyclopedia of Genes and Genomes pathways with direct or indirect role in cell/tissue development and metabolic processes were enriched for DEGs. Our results suggest that phenotypic differences between the two contrasting genotypes can be governed via regulation of hormone signal transduction/or cell cycle and stress‐related pathways. Several candidate genes for spine formation, early flowering, and drought tolerance were introduced, important instances are ZHD8 and TBL21 (candidates for spininess), three novel transcripts, respectively, encoding a CCT type protein, a MADS‐box TF and a CCA1 (candidates for early flowering), and CAT2, ZAT10, and CAMTA (candidates for drought response). These findings facilitate the isolation of key genes controlling drought‐tolerance, spininess, and early flowering in safflower and can be applied for developing value‐added varieties through genome‐based breeding programs.