Integrated physiological characters and transcriptome analyses reveal the expansion mechanism of lateral cormels of <i>Colocasia esculenta</i>

Multi-cormels taro is one of the main cultivation types of taro in southern China, and its yield and quality are largely determined by cormel expansion. Identifying the regulatory mechanisms related to multi-cormels taro cormel expansion would be useful for improving its yield and quality. In this study, Ganyu4, a mutant of multi-cormels taro with long rod-like cormels from the somatic variation during the tissue culture, and its wild type (Ganyu2, the lateral cormels are globular) were used as material, and the morphological and physiological characteristics of cormels in different developmental stages were investigated and determined after differentially expressed genes related to cormel expansion were screened using transcriptome sequencing analysis. The results showed that the external features of taro lateral cormel expansion were reflected in the continuous and uniform growth of transverse and longitudinal diameters in Ganyu2, and the internal features were reflected in the transverse growth of parenchyma cells, rapid growth of vascular bundles, and accumulation of starch granules. The positive correlations were detected between longitudinal diameter and GA₃ content, as well as between transverse growth and starch accumulation. Transcriptome profiling revealed key candidate DEGs involved in GA₃ synthesis and signal transduction, starch and sucrose metabolism, the cell cycle, and cell wall metabolism during taro cormel expansion. <italic>CeAGPase</italic> was verified to be a positive regulator of starch accumulation and may promote taro cormel expansion. These results provide novel insights into the molecular mechanisms underlying taro cormel expansion.