The development of functional mapping by three sex-related loci on the third whorl of different sex types of <i>Carica papaya</i> L.

<div><p><i>Carica papaya</i> L. is an important economic crop worldwide and is used as a model plant for sex-determination research. To study the different flower sex types, we screened sex-related genes using alternative splicing sequences (AS-seqs) from a transcriptome database of the three flower sex types, i.e., males, females, and hermaphrodites, established at 28 days before flowering using 15 bacterial artificial chromosomes (BACs) of <i>C</i>. <i>papaya</i> L. After screening, the cDNA regions of the three sex-related loci, including short vegetative phase-like (<i>CpSVPL</i>), the chromatin assembly factor 1 subunit A-like (<i>CpCAF1AL</i>), and the somatic embryogenesis receptor kinase (<i>CpSERK</i>), which contained eight sex-related single-nucleotide polymorphisms (SNPs) from the different sex types of <i>C</i>. <i>papaya</i> L., were genotyped using high-resolution melting (HRM). The three loci were examined regarding the profiles of the third whorl, as described below. <i>CpSVPL</i>, which had one SNP associated with the three sex genotypes, was highly expressed in the male and female sterile flowers (abnormal hermaphrodite flowers) that lacked the fourth whorl structure. <i>CpCAF1AL</i>, which had three SNPs associated with the male genotype, was highly expressed in male and normal hermaphrodite flowers, and had no AS-seqs, whereas it exhibited low expression and an AS-seqs in intron 11 in abnormal hermaphrodite flowers. Conversely, carpellate flowers (abnormal hermaphrodite flowers) showed low expression of <i>CpSVPL</i> and AS-seqs in introns 5, 6, and 7 of <i>CpSERK</i>, which contained four SNPs associated with the female genotype. Specifically, the <i>CpSERK</i> and <i>CpCAF1AL</i> loci exhibited no AS-seq expression in the third whorl of the male and normal hermaphrodite flowers, respectively, and variance in the AS-seq expression of all other types of flowers. Functional mapping of the third whorl of normal hermaphrodites indicated no AS-seq expression in <i>CpSERK</i>, low <i>CpSVPL</i> expression, and, for <i>CpCAF1A</i>L, high expression and no AS-seq expression on XY^h-type chromosomes.</p>