Identification And Expression Pattern Analysis Of MADS-box Gene Family In Hoya Carnosa

Hoya carnosa is a plant of the genus Hoya,belongs to the subfamily Asclepiadoideae of Apocynaceae.The flower structure of Hoya is complex and exquisite,which contain a corona,pistils and stamens united to form a gynostegium,pollen is sticky to form pollinia.The Hoya is one of the most complex morphological groups of flowering plants and as the ideal candidates for studying the evolution of the flower structure in angiosperm.The MADS-box gene family is considered to be a key gene family in plant reproductive growth and nutrient organ development,and play an important role in the development of flowering organs particularly.However,the MADS-box gene in Apocynaceae has not been reported.In this study,the MADS-box gene family screening and identification related to flower development was carried out in H.carnosa.In addition to this,the expression pattern of MADS-box gene in H.carnosa was analyzed to investigate the origin and evolution of special flower structures(paracoralla,pollinia,gynostemium,etc.).The main results are as following:1.The MADS-box gene family of H.carnosa was identified based on the whole-genome level,which 49 MADS-box members(numbered HcMADS01～HcMADS49)were found.Physicochemical properties analysis showed that the 49 MADS-box genes had a protein length of 108～776 aa,a molecular weight between 11.46～88.63 k Da and an average molecular weight of 26.89 k Da,an isoelectric point between 4.62～10.04.2.HcMADS genes could be divided into two subfamilies through homology comparison and phylogenetic analysis,of which type I contains 16 genes(12 Mα,1 Mβ,and 3 Mγ),and type II contains 33 genes(28 MIKCC and 5 MIKC*).The MADS-box gene of H.carnosa might also have undergone an evolutionary process from type II MIKCC genes to MIKC*genes to Mα,Mβ and Mγ genes.3.Through gene structure analysis,it showed that genes with similar phylogenetic relationships were generally more similar.Through protein motif amalysis,it found that in additionto the constituent motifs of the MADS-box and K-box domains,other motifs with unknown functions showed a similar specific distribution in the same MADS-box subfamily.The 49 MADS-box genes could be accurately mapped to the hypothetical physical map of 9chromosomes of H.carnosa.4.The expression pattern analysis showed that the retention of the AGL6 gene and the high expression of B,C,and E in the petals of the H.carnosa might made the evolve a special paracoralla that is different from other Apocynaceae plants.The MIKC* gene was associated with the pollinia formation.Thus,the HcMADS17 gene in the MIKC* branch and B,C,and E classes might jointly regulate the formation of pollinia in H.carnosa.The C/D class gene AG subfamily of H.carnosa was divided into two branches,and one of these branches,HcMADS23 gene,was highly expressed in gynostemium.There were also B and E genes that were highly expressed in the gynostegium.as a result,B+C/D+E class genes might jointly influence the formation of gynostemium in H.carnosa.This study investigates the origin and evolution of the special flower structure of H.carnosa by bioinformatic.The results could provide a basis for future work on flower development and evolution of Apocynaceae plants or support the molecular breeding of H.carnosa.