Datir Sagar S
Biology Department, Biosciences Complex, Queen's University, Kingston, Ontario, Canada.
Crit Rev Food Sci Nutr. 2021;61(22):3804-3818. doi: 10.1080/10408398.2020.1808876. Epub 2020 Aug 25.
Invertase inhibitors classified as cell wall/apoplastic and vacuolar belonging to the pectin methylesterase family, play a major role in cold-induced sweetening (CIS) process of potato tubers. The CIS process is controlled at the post-translational level via an interaction between invertase (cell wall/apoplastic and vacuolar) by their compartment-specific inhibitors (cell wall/apoplastic and vacuolar). Invertase inhibitors have been cloned, sequenced and functionally characterized from potato cultivars differing in their CIS ability. The secondary structure of the invertase inhibitors consisted of seven alpha-helices and four conserved cysteine residues. The well-conserved three amino acids i.e. Pro-Lys-Phe are known to interact with invertase. Location of the genes encoding cell wall/apoplastic and vacuolar invertase inhibitors on potato chromosome number twelve in a tandem orientation without any intervening genes suggest their divergence into the cell wall and vacuole forms following the event of gene duplication. Under cold storage conditions, the vacuolar invertase inhibitor gene showed developmentally regulated alternative splicing and produce hybrid mRNAs which were the result of mRNA splicing of an upstream region of vacuolar invertase inhibitor gene to a downstream region of the apoplastic invertase inhibitor gene. Transgenic potato tubers overexpressing invertase inhibitors resulted in decreased invertase activity, low reducing sugars and improved processing quality making invertase inhibitors highly potential candidate genes for overcoming CIS. Clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) gene-editing technology offers transgene-free breeding for developing CIS resistant potato cultivars. Moreover, the post-transcriptional regulation of invertase inhibitors during cold storage can be warranted. This review summarizes progress and current knowledge on biochemical and molecular approaches used for the understanding of invertase inhibitors with special reference to key findings in potato.
属于果胶甲酯酶家族的细胞壁/质外体和液泡型转化酶抑制剂，在马铃薯块茎的冷诱导糖化（CIS）过程中起主要作用。CIS过程在翻译后水平上通过转化酶（细胞壁/质外体和液泡型）与其特定区室抑制剂（细胞壁/质外体和液泡型）之间的相互作用来控制。已从CIS能力不同的马铃薯品种中克隆、测序并对转化酶抑制剂进行了功能表征。转化酶抑制剂的二级结构由七个α螺旋和四个保守的半胱氨酸残基组成。已知三个保守氨基酸即脯氨酸-赖氨酸-苯丙氨酸与转化酶相互作用。编码细胞壁/质外体和液泡型转化酶抑制剂的基因在马铃薯12号染色体上以串联方向排列，没有任何间隔基因，这表明它们在基因复制事件后分化为细胞壁和液泡形式。在冷藏条件下，液泡型转化酶抑制剂基因表现出发育调控的可变剪接，并产生杂种mRNA，这是液泡型转化酶抑制剂基因上游区域与质外体转化酶抑制剂基因下游区域mRNA剪接的结果。过表达转化酶抑制剂的转基因马铃薯块茎导致转化酶活性降低、还原糖含量降低并提高了加工品质，这使得转化酶抑制剂成为克服CIS的极具潜力的候选基因。成簇规律间隔短回文重复序列（CRISPR）/CRISPR相关蛋白9（Cas9）基因编辑技术为培育抗CIS的马铃薯品种提供了无转基因育种方法。此外，冷藏期间转化酶抑制剂的转录后调控也可以得到保证。本综述总结了用于理解转化酶抑制剂的生化和分子方法的进展及当前知识，并特别提及了马铃薯中的关键发现。
