Patterns of Expansion and Expression Divergence of the Polygalacturonase Gene Family in Brassica oleracea.

Meiling Lyu,Binghua Wu,Jiashu Cao,Rongfang Guo,Junaid Iftikhar

doi:10.3390/ijms21165706

Abstract

Plant polygalacturonases (PGs) are closely related to cell-separation events during plant growth and development by degrading pectin. Identifying and investigating their diversification of evolution and expression could shed light on research on their function. We conducted sequence, molecular evolution, and gene expression analyses of PG genes in Brassica oleracea. Ninety-nine B. oleracea PGs (BoPGs) were identified and divided into seven clades through phylogenetic analysis. The exon/intron structures and motifs were conserved within, but divergent between, clades. The second conserved domain (GDDC) may be more closely related to the identification of PGs. There were at least 79 common ancestor PGs between Arabidopsis thaliana and B. oleracea. The event of whole genome triplication and tandem duplication played important roles in the rapid expansion of the BoPG gene family, and gene loss may be an important mechanism in the generation of the diversity of BoPGs. By evaluating the expression in five tissues, we found that most of the expressed BoPGs in clades A, B, and E showed ubiquitous expression characteristics, and the expressed BoPGs in clades C, D, and F were mainly responsible for reproduction development. Most of the paralogous gene pairs (76.2%) exhibited divergent expression patterns, indicating that they may have experienced neofunctionalization or subfunctionalization. The cis-elements analysis showed that up to 96 BoPGs contained the hormone response elements in their promoters. In conclusion, our comparative analysis may provide a valuable data foundation for the further functional analysis of BoPGs during the development of B. oleracea.

Highlights

Pectin is the main component of the primary cell wall
Through a comprehensive analysis of the gene sequences, gene structures, molecular evolution, a single gene, and duplicated gene expression patterns, as well as subcellular localization of PG proteins, we provided a detailed characterization of the composition, expansion, and expression divergence of the PG gene family in B. oleracea
The Polygalacturonase Gene Family in B. oleracea Consists of 99 Members

Summary

Introduction

Pectin is the main component of the primary cell wall. Its degradation happens in a variety of periods of plant development, such as seed germination, organ abscission, fruit ripening, anther dehiscence, silique dehiscence, pollen development, pollen tube growth, and so on [1,2,3,4]. They can catalyze random hydrolysis and disassembly of the 1,4-α-D-galactosiduronic linkages of pectin, causing pectin degradation [5]. In Brassica rapa, the PGs BcMF2, BcMF6, BcMF16, BcMF17, and BcMF24 have been shown to play important roles in pollen development and pollen tube growth [9,10,11,12,13]. The PG gene BoMF25 in Brassica oleracea was proven to be related to the development of the pollen wall [14]. He et al [15] characterized the maize PG gene ZmPGH1 and demonstrated that it functions as a suppressor of programmed cell death in plants

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Results

Conclusion