Gene expression profiling before and after internode culture for adventitious shoot formation in ipecac

Area of Science:

• Plant biotechnology
• Molecular biology
• Plant development

Background:

• Adventitious shoots in ipecac (Carapichea ipecacuanha) are induced on internodal segments in phytohormone-free media.
• Shoot formation occurs specifically on the apical epidermis, not the basal region.
• Endogenous auxin and cytokinin levels transiently increase after one week of culture.

Purpose of the Study:

• To investigate gene expression patterns during adventitious shoot formation in ipecac.
• To compare gene expression between apical and basal regions of stem segments.
• To identify genes involved in shoot induction without callus formation.

Main Methods:

• RNA sequencing (RNA-seq) analysis of apical and basal stem segments.
• De novo assembly of the ipecac transcriptome.
• Quantitative real-time PCR (qRT-PCR) for gene expression validation.

Main Results:

• 8987 differentially expressed genes were identified out of 76,684 genes.
• 276 genes were upregulated in the apical region after one week of culture.
• Upregulated genes included 18 phytohormone-response and shoot-formation-related genes.

Conclusions:

• Cytokinin biosynthesis gene expression is induced in the apical region, correlating with cellular pluripotency.
• Wounding initiates cell division in the apical region, triggering direct adventitious shoot formation.
• The study elucidates a pathway for direct shoot regeneration in ipecac without callus intermediates.