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Fig. 3 | Genome Biology

Fig. 3

From: The spinach YY genome reveals sex chromosome evolution, domestication, and introgression history of the species

Fig. 3

Proposed mechanism for spinach sex determination and differentiation. a Expression pattern of genes within the SDR at early and late flower development stages between male and female flowers. Two Y-specific genes (YY20280, YY20279) are located in Insertion 1 flanking the largest Inversion 1. b Alignments of male and female Illumina reads to the YY genome revealed the presence/absence variants (PAV) NRT1/PTR 6.4 and EIF3-subunit A in male and female individuals, which confirmed them as Y-specific genes. c Visualization of Y-specific (NRT1/PTR6.4 and EIF3) genes in their first-degree gene network at stage 1 (S1). Gene clusters putatively related to different functions are indicated with different colors. The sizes of the nodes reflect the number of edges connected to other nodes in the network. d Proposed pathway for single-factor sex determination in spinach. NRT1/PTR6.4 can integrate two independent pathways to promote stamen initiation and suppress carpel development. The proteins encoded by the B-class (APETELA3, PISTILLATA) genes can function as intermediates in these pathways. These B-class genes might be activated by synergistic or independent action of hormones including gibberellins (GA) and jasmonates (JA). NRT1 may transport GA and JA to induce stamen initiation, thus repressing CRC expression, or inhibit the AG-KNU-WUS interaction, resulting in meristem termination failure and carpel suppression in male flowers (right side). A reverse process might occur in the absence of NRT1 gene and protein in female flowers (left side). In dioecious spinach, only male individuals with a Y-chromosome stably express NRT1. Black text refers to activation, while gray text refers to inhibition of the pathway

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