Genetic mechanisms of petal morphogenesis in Eustoma grandiflorum

Abstract

Eustoma grandiflorum, also known as lisianthus, is a popular ornamental plant belonging to the Gentianaceae family. Due to its diverse petal shapes, it is an excellent model for studying the genetic mechanisms of petal morphogenesis. In this study, we conducted a comparative morphological, anatomical, and transcriptional analysis of two cultivated varieties of lisianthus, ‘Wavy White’ with wavy petals and ‘Rosita White’ with flat petals. Cytological observations showed that the cells of both the epidermis (Ep) and parenchymatous tissue (Pt) at the bud stage, as well as the cell numbers of Ep at the mature stage existed difference between petals in ‘Rosita White’ and ‘Wavy White’. We found that genes involved in cell division, cell expansion, and microtubule-based processes, including genes in the CYCLIN D3 (CYCD3) family, EXPANSIN (EXP) family, and Tubulin/FtsZ family, were highly over-represented during the bud stage in ‘Wavy White’. At the bud stage, several specific genes, including EXP1, YABBY3 (YAB3), GROWTH-REGULATING FACTOR 1 (GRF1), LEAFY (LFY), LOB DOMAIN-CONTAINING PROTEIN 40 (LBD40), and PROTODERMAL FACTOR 2 (PDF2) were found to be highly expressed in the petals of ‘Wavy White’. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis further confirmed significantly higher expression levels of LFY, PDF2, GRF1, and YAB3 in ‘Wavy White’ than those in ‘Rosita White’ at the bud stage. And we found that YAB3 was more highly expressed in petals in lisianthus cultivars with wavy petals than those in ‘Rosita White’; LFY was more highly expressed in petals in lisianthus cultivars with wavy petals except ‘Wavy Purple’ than those in ‘Rosita White’. Overall, our findings shed light on the genetic mechanisms of petal morphogenesis in lisianthus.