Freezing Tolerance and Expression of β-amylase Gene in Two Actinidia arguta Cultivars with Seasonal Changes

Abstract

Low temperature causes injuries to plants during winter, thereby it affects kiwi fruit quality and yield. However, the changes in metabolites and gene expression during cold acclimation (CA) and deacclimation (DA) in kiwi fruit remain largely unknown. In this study, freezing tolerance, carbohydrate metabolism, and β-amylase gene expression in two Actinidia arguta cv. “CJ-1” and “RB-3” were detected from CA to DA stages. In all acclimation stages, the “CJ-1” was hardier than “RB-3” and possessed lower semi-lethal temperature (LT50). Furthermore, “CJ-1” had a more rapid acclimation speed than “RB-3”. Changes of starch, β-amylase, and soluble sugars were associated with freezing tolerance in both cultivars. Starch contents continued to follow a declining trend, while soluble sugars contents continuously accumulated in both cultivars during CA stages (from October to January). To investigate the possible molecular mechanism underlying cold response in A. arguta, in total, 16 AcBAMs genes for β-amylase were identified in the kiwi fruit genome. We carried out localization of chromosome, gene structure, the conserved motif, and the analysis of events in the duplication of genes from AcBAMs. Finally, a strong candidate gene named AaBAM3 from AcBAMs was cloned in Actinidia arguta (A. arguta), The real-time qPCR showed that AaBAM3 gene expression in seasonal changes was consistent with changes of soluble sugars. These results reveal that AaBAM3 may enhance the freezing tolerance of A. arguta through increasing soluble sugar content.

The AaCBF4-AaBAM3.1 module enhances freezing tolerance of kiwifruit (Actinidia arguta)

“…MT263012) from A. arguta . AaBAM3.1 had a full - length ORF of 1644 bp flanking a 1363 bp promoter 23 . AaBAM3.1 encoded a protein of 548 amino acids with a 61.74 kDa molecular weight, and the theoretical isoelectric point of AaBAM3.1 was 8.76.…”

“…We have now acquired detailed information about BAMs, which have been shown to play key roles in response to abiotic stress by degrading starch 22 . BAMs are members of glycosyl hydrolase family 14 (PF01373) and have two typical catalytic sites at the N-terminus and in a central location; thus, these enzymes can hydrolyze 1,4-alpha-glucosidic linkages within starch 23 . BAMs are considered to be the mediators that degrade starch into downstream soluble sugars and play a pivotal role in the accumulation of soluble sugars under cold stress.…”

Genome-wide identification of BAM (β-amylase) gene family in jujube (Ziziphus jujuba Mill.) and expression in response to abiotic stress

“…Its degradation is intimately associated with fruit ripening and metabolism [ 47 , 48 ]. BAM modulates starch degradation, participates in plant sugar metabolism, and responds to abiotic stress [ 20 ]. Numerous BAM genes are involved in plant stress response.…”

“…Meanwhile, BAM4 controls starch metabolism and is differentially regulated among various species [ 19 ]. BAM genes also play pivotal roles in abiotic stress tolerance by degrading starch and regulating soluble sugar accumulation in response to cold stress [ 20 – 22 ]. Considering that BAM gene expression and BAM protein activity are elevated in pear, blueberry, orange, tea tree, potato, and poplar under cold stress [ 23 – 28 ], this gene family may play key regulatory roles in jujube response to abiotic stress.…”

Full-length transcriptome profiling reveals insight into the cold response of two kiwifruit genotypes (A. arguta) with contrasting freezing tolerances

“…The expression and activity of BAM were reported to be significantly induced after a 6 h treatment of cold stress in A. thaliana [ 53 ]. In kiwifruit, AaBAM3 was upregulated to increase the activity of beta-amylase from autumn to winter in China [ 54 ]. In pear, researchers have found the same results as those in kiwifruit [ 55 ].…”