Comparative physiological and transcriptomic analysis reveal MdWRKY75 associated with sucrose accumulation in postharvest ‘Honeycrisp’ apples with bitter pit

Abstract

Background Calcium (Ca) deficiency can cause apple bitter pit, reduce the quality and shelf life. WRKY transcription factors play essential role in plant response to multiple disorders. However, the underlying mechanisms causing bitter pit in apple fruit due to Ca deficiency during storage is extremely limited. Results In the present study, the nutritional metabolites and reactive oxygen species (ROS) were compared in Ca-deficient and healthy apple fruit (CK) during storage. Results showed that Ca-deficient apples sustained significantly higher production of ROS, PPO activity, flavonoids, total phenol, total soluble solids (TSS), and sucrose contents, but the contents of Ca, H2O2, titratable acids (TA), glucose and fructose were significantly lower than those of CK during storage. Principal component analysis (PCA) showed that TSS, •O2−, PPO, malondialdehyde (MDA) and Ca were the main factors, and TSS had a positive correlation with sucrose. Furthermore, transcriptome analysis revealed that WRKYs were co-expressed with sucrose metabolism-related enzymes (SWEETs, SS, SPS). qRT-PCR and correlation analysis indicated that MdWRKY75 was correlated positively with MdSWEET1. Moreover, transient overexpression of MdWRKY75 could significantly increase the sucrose content and promote the expression of MdSWEET1 in apple fruit. Conclusions Calcium deficiency could decrease antioxidant capacity, accelerate nutritional metabolism and up-regulate the expression of WRKYs in apple with bitter pit. Overexpression of MdWRKY75 significantly increased sucrose accumulation and the expression of MdSWEET1. These findings further strengthened knowledge of the basic molecular mechanisms in calcium deficiency apple flesh and contributed to improving the nutritional quality of apple fruit.

Mechanism of improving the quality of table grapes (Vitis. spp.) by exogenous eugenol based on transcriptome

“…Similarly, Sun et al . (2022) displayed the transient overexpression of MdWRKY75 can dramatically enhance the sucrose content and facilitate the expression of MdSWEET1 in apple fruits. However, PpWRKY46 and PpWRKY53 were up‐ and downregulated, respectively, by methyl jasmonate treatment in peaches (Ji et al ., 2022).…”

“…Exogenous treatment (b-aminobutyric acid, methyl jasmonate, and benzothiadiazole) upregulated PpWRKY40 expression; it is a transcriptional activator of sucrose synthase (PpSS1) and sucrose phosphate synthase (PpSPS3)related genes in peach postharvest fruit sucrose synthesis (Wang et al, 2023). Similarly, Sun et al (2022) displayed the transient overexpression of MdWRKY75 can dramatically enhance the sucrose content and facilitate the expression of MdSWEET1 in apple fruits. However, PpWRKY46 and PpWRKY53 were up-and downregulated, respectively, by methyl jasmonate treatment in peaches (Ji et al, 2022).…”

Transcriptome and Metabolome Analyses Reveal Sugar and Acid Accumulation during Apricot Fruit Development

“…The studies on the sugar metabolism of Rosaceae fruit trees mainly focus on the peach [8][9][10], apricot [11][12][13], plum [14][15][16], cherry [17,18], apple [19][20][21], pear [22,23], and loquat [24]. Sucrose, fructose, glucose, and sorbitol were found to be the main sugars accumulated in the fruits of the Roseaceae family [25].…”