Transcriptomic analysis related to the flowering of the citrus hybrid Microcitrangemonia

Abstract

Flowering in citrus plants grown from seeds occurs between four to ten years; therefore, the reduction of the juvenile period is a challenge for the genetic improvement of citrus. However, the Embrapa Mandioca e Fruticultura created a hybrid called Microcitrangemonia [Lemon Tree 'Rangpur' (LCR) X Citrus 'Yuma' (CTYM) – 005) X Microcitrus papuana (MCP) – 011] which presents a short juvenile period (one year) and flowering in all seasons of the year. It has a rare genotype for citrus cultivation. Other varieties with similar characteristics are only transgenic. This work describes the genes expressed in flowering-related pathways in the citrus hybrid Microcitrangemonia, which shows early and constant flowering and compares the gene function of each pathway with the existing Arabidopsis thaliana homologues. We performed RNA extraction, RNA-sequence library construction and sequencing from leaves, reproductive buds and stems of the H011 plant. We identified flowering-related transcripts and cladograms of similarity for the SOC1, AP1 and FLC proteins. Sequence annotation showed that most of the hits are similar to Citrus sinensis, 57%, and Citrus clementina, 38.9%. Different sequences similar to 29 proteins belonging to different flowering-related pathways have been identified, such as gibberellin, photoperiod, autonomous and vernalization. The analysis of similarity allowed inferring that H011 has greater evolutionary kinship with Citrus sinensis. The outcomes contribute to the understanding of the early and constant flowering of H011 as well as provide an important resource for breeding programs in citrus aimed at juvenile period reduction.