香蕉果实可溶性淀粉合成酶基因MaSSIII-1的分子特征与时空表达模式

为弄清香蕉果实可溶性淀粉合成酶基因(MaSSIII-1)的分子特征及时空表达模式,以‘巴西蕉’果肉为试材,采用PCR法进行MaSSIII-1基因克隆,通过Quantitative real-time PCR (qPCR)和Western blot技术对MaSSIII-1基因及其蛋白表达模式进行分析。结果显示：MaSSIII-1基因cDNA全长为2397 bp,编码798 个氨基酸,包括4 个典型的结构域,GenBank 登录号为KU757067。MaSSIII-1 基因在香蕉根、球茎、花和苞片中表达量较低,在叶、果皮和果肉中表达量较高;随着香蕉果实发育,MaSSIII-1 基因表达量逐渐上升,在抽蕾后50~60 天达到最大;随着果实采后成熟,MaSSIII-1 表达量在采后5 天达到最大,随后逐渐下降。在香蕉果实不同发育及采后成熟阶段,MaSSIII-1 蛋白呈现出与mRNA水平相一致的表达趋势。证明MaSSIII-1 基因的表达不仅涉及到香蕉果实支链淀粉合成代谢,可能还涉及采后早期果实成熟或者支链淀粉降解。

Molecular Characteristics and Temporal and Spatial Expression Patterns of Soluble Starch Synthase III-1 Gene (MaSSIII-1) in Banana (Musa acuminata) Fruit

To clarify the molecular characteristics and temporal and spatial expression patterns of soluble starch synthase III-1 gene (MaSSIII-1), using the‘Brazilian’banana pulps as the test material, the MaSSIII-1 gene was cloned by PCR method. Quantitative real-time PCR (qPCR) and Western blot technology were used to analyze MaSSIII- 1 gene and its protein expression pattern. The results showed that the cDNA full-length of MaSSIII-1 gene (accession No. KU757067) was 2397 bp encoding 798 amino acids with four typical domains. The expression level of MaSSIII-1 was low in roots, bulbs, flowers, and bracts, but it exhibited high expression in leaves, peels, and pulps. Moreover, MaSSIII- 1 expression increased gradually with banana fruit development, and then reached the highest expression in 50-60 d after emergence from the pseudostem. The expression level of MaSSIII-1 reached the maximum value in 5 d after harvest and then decreased gradually during postharvest ripening in banana fruit. The expression pattern of MaSSIII-1 protein was consistent with the expression trend at mRNA level during banana fruit development and ripening. These results suggested that the expression of MaSSIII- 1 gene may involve not only amylopectin biosynthesis but also early fruit ripening or amylopectin degradation in banana.