Identification and expression analysis of BoMF25, a novel polygalacturonase gene involved in pollen development of Brassica oleracea

Abstract

BoMF25 acts on pollen wall. Polygalacturonase (PG) is a pectin-digesting enzyme involved in numerous plant developmental processes and is described to be of critical importance for pollen wall development. In the present study, a PG gene, BoMF25, was isolated from Brassica oleracea. BoMF25 is the homologous gene of At4g35670, a PG gene in Arabidopsis thaliana with a high expression level at the tricellular pollen stage. Collinear analysis revealed that the orthologous gene of BoMF25 in Brassica campestris (syn. B. rapa) genome was probably lost because of genome deletion and reshuffling. Sequence analysis indicated that BoMF25 contained four classical conserved domains (I, II, III, and IV) of PG protein. Homology and phylogenetic analyses showed that BoMF25 was clustered in Clade F. The putative promoter sequence, containing classical cis-acting elements and pollen-specific motifs, could drive green fluorescence protein expression in onion epidermal cells. Quantitative RT-PCR analysis suggested that BoMF25 was mainly expressed in the anther at the late stage of pollen development. In situ hybridization analysis also indicated that the strong and specific expression signal of BoMF25 existed in pollen grains at the mature pollen stage. Subcellular localization showed that the fluorescence signal was observed in the cell wall of onion epidermal cells, which suggested that BoMF25 may be a secreted protein localized in the pollen wall.

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

“…Moreover, the BoPG Bol018697 that belonged to clade F was dominantly expressed in Bud 5 in our result. This BoPG has been demonstrated to be closely related to pollen development by in situ hybridization and promoter expression analysis [ 14 ]. The possible functions of other BoPGs, especially the genes with higher expression levels, need further study.…”

“…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 ]. Recently, He et al [ 15 ] characterized the maize PG gene ZmPGH1 and demonstrated that it functions as a suppressor of programmed cell death in plants.…”

Transcriptome profiling of differentially expressed genes in floral buds and flowers of male sterile and fertile lines in watermelon

“…Genes related to cell wall loosening were prominently expressed in DAH3615 and included in cluster 7 such as polygalacturonase (PG), expansins, pectate lyase, cellulase (glycosyl hydrolase family 5), endoglucanase, and glucan endo-1 3-beta-glucosidase 5. PG is involved in anther dehiscence [ 60 , 61 ], pollen mother cell wall degradation [ 62 ], pollen intine and exine formation [ 63 ], and pollen tube growth [ 64 ], while pectate lyase in pollen wall development [ 65 , 66 ] and pollen tube growth [ 67 , 68 ]. In this study, male-sterile flowers did not produce any pollen, since many genes related to pollen formation, development, and pollen tube growth were distinguishably expressed in the floral buds and flowers of DAH3615, but not in those of DAH3615-MS.…”

Establishment and optimization of mRNA in situ hybridization system in turnip (Brassica rapa var. rapa)

“…The ideal probe concentration will obtain good signal. In general, the probe concentration is controlled between 100 and 600 ng/ml in ISH [20, 21]. Some researchers suggested that the optimal probe concentration is related to the probe length and should be kept at 0.5 ng/µl/kb [22].…”