Soluble Starch Synthase III-1 in Amylopectin Metabolism of Banana Fruit: Characterization, Expression, Enzyme Activity, and Functional Analyses

Abstract

Soluble starch synthase (SS) is one of the key enzymes involved in amylopectin biosynthesis in plants. However, no information is currently available about this gene family in the important fruit crop banana. Herein, we characterized the function of MaSSIII-1 in amylopectin metabolism of banana fruit and described the putative role of the other MaSS family members. Firstly, starch granules, starch and amylopectin content were found to increase during banana fruit development, but decline during storage. The SS activity started to increase later than amylopectin and starch content. Secondly, four putative SS genes were cloned and characterized from banana fruit. Among them, MaSSIII-1 showed the highest expression in banana pulp during fruit development at transcriptional levels. Further Western blot analysis suggested that the protein was gradually increased during banana fruit development, but drastically reduced during storage. This expression pattern was highly consistent with changes in starch granules, amylopectin content, and SS activity at the late phase of banana fruit development. Lastly, overexpression of MaSSIII-1 in tomato plants distinctly changed the morphology of starch granules and significantly increased the total starch accumulation, amylopectin content, and SS activity at mature-green stage in comparison to wild-type. The findings demonstrated that MaSSIII-1 is a key gene expressed in banana fruit and responsible for the active amylopectin biosynthesis, this is the first report in a fresh fruit species. Such a finding may enable the development of molecular markers for banana breeding and genetic improvement of nutritional value and functional properties of banana fruit.

Emerging Applications of Fermented Fruit Enzyme Beverages as Nutraceutical, Functional Food, and Designer Food Products: A Review

“…Further Western blot analysis suggested that the protein was gradually increased during banana fruit development, but drastically reduced during storage. Lastly, over expression of MaSSIII-1 in tomato plants distinctly changed the morphology of starch 67 .Chemical constituents, radical scavenging activity and enzyme inhibitory capacity of fruits from Cotoneaster pannosus Franch. Cotoneaster pannosus (Rosaceae) is a semievergreen shrub, producing globose dark red pomes, native to China and widely used as an ornamental plant all over the world.…”

Expression Fluctuations of Genes Involved in Carbohydrate Metabolism Affected by Alterations of Ethylene Biosynthesis Associated with Ripening in Banana Fruit

“…During the development of a banana, starch and amylopectin accumulate gradually and starch’s synthase (SS; EC2.4.1.21) activity increases until the late stage, remaining constant during starch breakdown (climacteric). However, it almost vanishes during storage and is accompanied by amylopectin and starch granule degradation [ 6 ]. Only β-amylase (EC3.3.1.2) activity increased before onset of the respiration peak and along with starch decrease.…”

“…The expression level of SPS increased distinctly but showed a very low activity at the onset of the climacteric stage and then steadily increased during the post climacteric stages. Moreover, little content of Fructose 2,6-bisphosphate (Fru(1,6)P2; EC3.1.3.46) was found in unripe fruit but increased markedly with an increased respiration rate [ 6 ]. The expression of uridine diphosphoryl (UDP)-glucose pyrophosphorylase (UGPase, EC2.7.7.9) in banana pulp was higher than that in peel and consistent with starch degradation and sucrose synthesis in pulp.…”

The AGPase Family Proteins in Banana: Genome-Wide Identification, Phylogeny, and Expression Analyses Reveal Their Involvement in the Development, Ripening, and Abiotic/Biotic Stress Responses

“…Starch is the most abundant storage polysaccharide in plants. As an important carbohydrate and energy source in the human diet and nutrition, starch is massively produced in cassava ( Manihot esculenta ) roots [ 1 ], potato ( Solanum tuberosum ) tubers [ 2 ], cereal seeds [ 3 ], and a number of fresh fruits such as banana ( Musa acuminata ) [ 4 , 5 , 6 , 7 , 8 ]. The biosynthesis of starch in plants is a complex process involving a variety of enzymes, such as ADP-glucose pyrophosphorylase (AGPase), granule-bound starch synthase (GBSS), soluble starch synthase (SS), starch branching enzyme (SBE), and debranching enzyme (DBE) [ 2 , 9 , 10 ].…”

“…With starch content reaching 74–88% of its dry weight in unripe fruit, M. acuminata is not only the most popular starch-rich fresh fruit in the world, but also an important staple food in some African and Latin American countries [ 6 , 7 , 8 , 33 , 34 ]. Starch biosynthesis is of crucial importance since starch content determines fruit yield, quality, and economic value of banana.…”