Characterization of the ABC Transporter G Subfamily in Pomegranate and Function Analysis of PgrABCG14

Abstract

ATP-binding cassette subfamily G (ABCG) proteins play important roles in plant growth and development by transporting metabolites across cell membranes. To date, the genetic characteristics and potential functions of pomegranate ABCG proteins (PgrABCGs) have remained largely unknown. In this study, we found that 47 PgrABCGs were divided into five groups according to a phylogenetic analysis; groups I, II, III, and IV members are half-size proteins, and group V members are full-size proteins. PgrABCG14, PgrABCG21, and PgrABCG47 were highly expressed in the inner seed coat but had very low expression levels in the outer seed coat, and the expression levels of these three PgrABCG genes in the inner seed coats of hard-seeded pomegranate ‘Dabenzi’ were higher than those of soft-seeded pomegranate ‘Tunisia’. In addition, the expression of these three PgrABCG genes was highly correlated with the expression of genes involved in lignin biosynthesis and hormone signaling pathways. The evolution of PgrABCG14 presents a highly similar trend to the origin and evolution of lignin biosynthesis during land plant evolution. Ectopic expression of PgrABCG14 in Arabidopsis promoted plant growth and lignin accumulation compared to wild type plants; meanwhile, the expression levels of lignin biosynthesis-related genes (CAD5, C4H, and Prx71) and cytokinin response marker genes (ARR5 and ARR15) were significantly upregulated in transgenic plants, which suggests the potential role of PgrABCG14 in promoting plant growth and lignin accumulation. Taken together, these findings not only provide insight into the characteristics and evolution of PgrABCGs, but also shed a light on the potential functions of PgrABCGs in seed hardness development.

Identification and Functional Analysis of CAD Gene Family in Pomegranate (Punica granatum)

“…In our study, most PgCAD gene structures in group II were consistent with pattern I, the PgCAD gene structure of group I (PgCAD7, PgCAD18) was consistent with pattern II, the members of groups III and IV were consistent with pattern III, and PgCAD10 and PgCAD13 did not fall into any of these three modes. Similar findings were found for CAD genes in other species [28,39].…”

“…The seed hardness of pomegranate is positively correlated with the lignin content. Reducing the lignin content can significantly reduce the seed hardness [39]. CAD catalyzes the last step of lignin synthesis and is an important indicator of lignin content.…”

Haplotype‐resolved genomes of octoploid species in Phyllanthaceae family reveal a critical role for polyploidization and hybridization in speciation

“…A similar increase in gene copy number is also found in the downstream ABC transporter family ( Pc : 54, Sa : 187, Pe : 318, Ss : 299) (Miao & Liu, 2010). In both polyploidies, we detected about three times ( Pe : 30, Ss :31, Sa : 28, Pc :10) increase of the gene copy number in this subfamily‐G of ABC family which was reported to participate in the monomers transport in suberin lamellae development and lignin accumulation (Yadav et al., 2014; Yu et al., 2022). Over 90% of these genes exhibit expression in either the leaves or stems.…”

Genome-Wide Identification of the ABC Gene Family and Its Expression in Response to the Wood Degradation of Poplar in Trametes gibbosa

“…For example, de Lima et al found that the ABC gene (Sv-ABCG17) is a potential transporter of lignin monomers [25]. Yu et al suggested the potential role of the ABC gene (PgrABCG14) in promoting plant growth and lignin accumulation [26]. Xie et al identified ABC family genes in Phanerochaete chryso-sporium and suggested that the transporter protein identified in the P. chrysosporium secretomes could play a role in cellobiose and/or cellodextrin uptake [27].…”