Genome-wide identification and expression analysis of MADS-box family genes in litchi (Litchi chinensis Sonn.) and their involvement in floral organogenesis II

Litchi possesses unique flower morphology and adaptive reproduction strategies. Although previous attention has been intensively devoted to the mechanisms underlying its floral induction, the molecular basis of flower organ development remains largely unknown. MADS-box genes are promise candidates for this due to their significant roles in various aspects of inflorescence and flower organogenesis. Here, we present a detailed overview of phylogeny and expression profiles of 101 MADS-box genes that were identified in litchi. These LcMADSs are unevenly located across the 15 chromosomes, and can be divided into type I and type II genes. Fifty type I MADS-box genes are sub-divided into Mα, Mβ and Mγ subgroups, while fifty-one type II LcMADSs consist of 37 MIKCC -type and 14 MIKC*-type genes. Both two types of LcMADS genes mainly contain ABA and MeJA response elements. Tissue-specific and development-related expression analysis reveals that LcMADS51 could be positively involved in litchi carpel formation, while six MADS-box genes including LcMADS42/46/47/75/93/100 play a possible role in stamen development. GA is positively involved in the sex determination of litchi flowers by regulating the expression of LcMADS75 (LcAP1) and LcMADS51 (LcSTK). However, JA probably plays a negative role in litchi flower development. Analysis of MADS-box gene expression at different developmental stages in female and male litchi flowers