Integrated QTL mapping and transcriptome analysis reveals the genetic and molecular mechanisms determining the development of pistillate lines in castor (Ricinus communis L.)

Castor ( Ricinus communis L.) is an important industrial crop for energy oil production. Its pistillate line is critical for heterosis utilization, but its genetic and molecular mechanisms are still poorly understood. In this study, we performed a classical Mendelian genetic analysis on two groups of multi-generation castor populations, revealing that the completely pistillate lines are controlled by four pairs of recessive genes with cumulative effects (genotype g 1 g 1 g 2 g 2 g 3 g 3 g 4 g 4 ). When the first three pairs of genes are homozygous recessive and the fourth pair is either heterozygous or homozygous dominant (genotype g 1 g 1 g 2 g 2 g 3 g 3 G 4 _), the castor plant develops into an incompletely pistillate line, characterized by the primary raceme exhibiting pistillate characteristics and some branch racemes developing into normal monoecious structures, resulting in a "sex reversal" phenomenon. At the same time, quantitative trait locus (QTL) mapping identified six QTLs associated with PC, which showed partial overlap. Transcriptome analysis revealed numerous differentially expressed genes (DEGs) involved in plant hormone signal transduction and the MAPK signaling pathway. Subsequently, by integrating transcriptome data, two candidate genes were identified within the relevant QTL regions. Ultimately, the key gene RcGT ( 29916.m000523 / LOC8265549 ), a member of the glycosyltransferase family, was confirmed to influence the development of pistillate lines through quantitative real-time polymerase chain reaction (qRT-PCR) and virus-induced gene silencing (VIGS). This gene likely affects plant hormone homeostasis by modifying specific substrates in the plant hormone metabolism pathway via glycosylation, thereby regulating the morphological development of the raceme in pistillate lines. Overall, this study provides a robust theoretical foundation for further research into gene function and systematic analysis of molecular mechanisms determining the development of pistillate lines in castor. • The completely pistillate lines are controlled by four pairs of recessive genes with cumulative effects. • The incompletely pistillate lines, a "sex reversal" phenomenon, are controlled by the genotype g 1 g 1 g 2 g 2 g 3 g 3 G 4 _. • A key glycosyltraferases gene RcGT (LOC8265549) that influences the development of castor pistillate lines was identified.