Genome-wide identification and expression analysis of the polygalacturonase gene family in sweetpotato.

BACKGROUND: Polygalacturonase (PG), a crucial enzyme involved in pectin degradation, is associated with various plants' developmental and physiological processes such as seed germination, fruit ripening, fruit softening and plant organ abscission. However, the members of PG gene family in sweetpotato (Ipomoea batatas) have not been extensively identified. RESULTS: In this study, there were 103 PG genes identified in sweetpotato genome, which were phylogenetically clustered into divergent six clades. The gene structure characteristics of each clade were basically conserved. Subsequently, we renamed these PGs according to their locations of the chromosomes. The investigation of collinearity between the PGs in sweetpotato and other four species, contained Arabidopsis thaliana, Solanum lycopersicum, Malus domestica and Ziziphus jujuba, revealed important clues about the potential evolution of the PG family in sweetpotato. Gene duplication analysis showed that IbPGs with collinearity relationships were all derived from segmental duplications, and these genes were under purifying selection. In addition, each promoter region of IbPG proteins contained cis-acting elements related to plant growth and development processes, environmental stress responses and hormone responses. Furthermore, the 103 IbPGs were differentially expressed in various tissues (leaf, stem, proximal end, distal end, root body, root stalk, initiative storage root and fibrous root) and under different abiotic stresses (salt, drought, cold, SA, MeJa and ABA treatment). IbPG038 and IbPG039 were down-regulated with salt, SA and MeJa treatment. According to the further investigation, we found that IbPG006, IbPG034 and IbPG099 had different patterns under the drought and salt stress in fibrous root of sweetpotato, which provided insights into functional differences among these genes. CONCLUSION: A total of 103 IbPGs were identified and classified into six clades from sweetpotato genome. The results of RNA-Seq and qRT-PCR suggested that IbPG006, IbPG034 and IbPG099 might play a significant role in tissue specificity as well as drought and salt stress responses, which showed valuable information for further functional characterization and application of the IbPGs.

Genome-Wide Identification and Expression Analysis of the Xyloglucan Endotransglucosylase/Hydrolase Gene Family in Sweet Potato [Ipomoea batatas (L.) Lam].

The xyloglucan endotransglucosylase/hydrolase (XET/XEH, also named XTH) family is a multigene family, the function of which plays a significant role in cell-wall rebuilding and stress tolerance in plants. However, the specific traits of the XTH gene family members and their expression pattern in different tissues and under stress have not been carried out in sweet potato. Thirty-six XTH genes were identified in I. batatas, all of which had conserved structures (Glyco_hydro_16). Based on Neighbor-Joining phylogenetic analysis the IbXTHs can be divided into three subfamilies-the I/II, IIIA, and IIIB subfamilies, which were unevenly distributed on 13 chromosomes, with the exception of Chr9 and Chr15. Multiple cis-acting regions related to growth and development, as well as stress responses, may be found in the IbXTH gene promoters. The segmental duplication occurrences greatly aided the evolution of IbXTHs. The results of a collinearity analysis showed that the XTH genes of sweet potato shared evolutionary history with three additional species, including A. thaliana, G. max, and O. sativa. Additionally, based on the transcriptome sequencing data, the results revealed that the IbXTHs have different expression patterns in leaves, stems, the root body (RB), the distal end (DE), the root stock (RS), the proximal end (PE), the initiative storage root (ISR), and the fibrous root (FR), and many of them are well expressed in the roots. Differentially expressed gene (DEG) analysis of FRs after hormone treatment of the roots indicated that IbXTH28 and IbXTH30 are up-regulated under salicylic acid (SA) treatment but down-regulated under methyl jasmonate (MeJA) treatment. Attentionally, there were only two genes showing down-regulation under the cold and drought treatment. Collectively, all of the findings suggested that genes from the XTH family are crucial for root specificity. This study could provide a theoretical basis for further research on the molecular function of sweet potato XTH genes.

Effect of Heat Treatment on the Quality and Soft Rot Resistance of Sweet Potato during Long-Term Storage.

Heat treatment is a widely applied technique in the preservation of fruits and vegetables, effectively addressing issues such as disease management, rot prevention, and browning. In this study, we investigated the impact of heat treatment at 35 °C for 24 h on the quality characteristics and disease resistance of two sweet potato varieties, P32/P (Ipomoea batatas (L.) Lam. cv 'Pushu13') and Xinxiang (Ipomoea batatas (L.) Lam. cv 'Xinxiang'). The growth in vitro and reproduction of Rhizopus stolonifer were significantly inhibited at 35 °C. However, it resumed when returned to suitable growth conditions. The heat treatment (at 35 °C for 24 h) was found to mitigate nutrient loss during storage while enhancing the structural characteristics and free radical scavenging capacity of sweet potato. Additionally, it led to increased enzyme activities for APX, PPO, and POD, alongside decreased activities for Cx and PG, thereby enhancing the disease resistance of sweet potato against soft rot. As a result, the heat treatment provided a theoretical basis for the prevention of sweet potato soft rot and had guiding significance for improving the resistance against sweet potato soft rot.