Genome-wide identification of mango (Mangifera indica L.) polygalacturonases: Expression analysis of family members and total enzyme activity during fruit ripening

Authors: DAUTT-CASTRO, MITZUKO - Centro De Investigacion En Alimentaction Y Desarollo; LOPEZ-VIRGEN, ANDRES - Centro De Investigacion En Alimentaction Y Desarollo; OCHOA-LEYVA, ADRIAN - Institute For Biotechnology - Mexico; CONTRERAS-VERGARA, CARMEN - Centro De Investigacion En Alimentaction Y Desarollo; SORTILLON-SORTILLON, ANA - Centro De Investigacion En Alimentaction Y Desarollo; MARTINEZ-TELLEZ, MIGUEL - Centro De Investigacion En Alimentaction Y Desarollo; GONZALEZ-AGUILAR, GUSTAVO - Centro De Investigacion En Alimentaction Y Desarollo; CASAS-FLORES, SERGIO - Instituto Potosino De Investigacion Cientifica Y Technology; SAÑUDO-BARAJAS, ADRIANA - Institute For Biotechnology - Mexico; Kuhn, David; ISLAS-OSUNA, MARIA - Centro De Investigacion En Alimentaction Y Desarollo

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2019
Publication Date: 7/30/2018
Citation: Dautt-Castro, M., Lopez-Virgen, A.G., Ochoa-Leyva, A., Contreras-Vergara, C.A., Sortillon-Sortillon, A.P., Martinez-Tellez, M.A., Gonzalez-Aguilar, G.A., Casas-Flores, S., Sañudo-Barajas, A., Kuhn, D.N., Islas-Osuna, M.A. 2018. Genome-wide identification of mango (Mangifera indica L.) polygalacturonases: Expression analysis of family members and total enzyme activity during fruit ripening. Frontiers in Plant Science. 10: 969. https://doi.org/10.3389/fpls.2019.00969.
DOI: https://doi.org/10.3389/fpls.2019.00969

Interpretive Summary: The United States is the number one importer of mango, most coming from Mexico. Prior to importation, mango must be given a hot water treatment of 30 minutes in 65o C water. It is well known that this treatment has deleterious effects on mango flavor, rate of ripening and shelf life. Polygalacturonases (PG) are enzymes that break down cell walls. This is a natural part of fruit ripening. This study compares the induction and activity of PG during ripening in hot water treated and untreated mango. Only some of the PG are transcriptionally activated by hot water treatment and contribute to the faster ripening and reduced shelf life due to the treatment. Using genomics approaches, these PG have been identified. This research will be useful to commercial producers of mango, importers and mango consumers.

Technical Abstract: Mango (Mangifera indica L.) is an important commercial fruit that shows a noticeable loss of firmness during ripening. Polygalacturonase (PG, E.C. 3.2.1.15) is a crucial enzyme for cell wall loosening during fruit ripening since it solubilizes pectin; therefore, PG activity correlates with fruit softening. Mango PGs were mapped to a genome draft from previously identified PGs from mango transcriptomes. From RNA-seq we have previously reported seventeen PGs whereas from in-depth genome analysis we identified 48 bonafide PGs. Phylogenetic analysis of the 48 mango PGs suggests that they are related to Citrus sinensis, which may indicate a recent evolutive divergence and related functions with orthologs in the tree. Expression analysis and total enzymatic activity were performed for PG transcripts expressed in mango cv. Kent mesocarp during postharvest ripening and nine PGs were differentially expressed during fruit ripening. According to the expression data, MiPG21-1, MiPG14, MiPG69-1, MiPG17, MiPG49, MiPG23-3, MiPG22-7 and MiPG16 were highly up-regulated during fruit ripening. These results correlate with a drastic loss of firmness observed in mangoes at day 10 during post-harvest, between the ethylene production burst and the climacteric peak. MiPG69-1 and MiPG23-3 had very high expression levels at day 16 of post-harvest storage, and those could be related to senescence; as well as MiPG17 and MiPG49, but with lower values. Meanwhile, MiPG46-3 was down-regulated during fruit ripening, most likely having a function in an earlier developmental stage. Total PG enzymatic activity was increased during ripening, having maximum levels at day 16 of post-harvest storage, these results correlated with a peak in gene expression of eight PGs. Moreover, analysis of intergenic regions showed important regulatory sequences associated to ripening in PGs such as MADS-box as well as those associated to ethylene regulation as ethylene insensitive 3 (EIN3) like factors, APETALA2-like transcription factors, and ethylene response element factors. Therefore, during mango fruit ripening the action of at least these PG genes contribute to softening, and their expression is regulated at the transcriptional level. Further biotechnological approaches to prolong mango postharvest shelf life could be targeted at specific PGs proposed in this work.