Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture, Wuhan 430070, People's Republic of China.
National Center for Vegetable Improvement (Central China), Wuhan 430070, People's Republic of China.
J Exp Bot. 2017 Apr 1;68(9):2317-2331. doi: 10.1093/jxb/erx076.
Cold-induced sweetening (CIS) in potato is detrimental to the quality of processed products. Conversion of starch to reducing sugars (RS) by amylases is considered one of the main pathways in CIS but is not well studied. The amylase genes StAmy23, StBAM1, and StBAM9 were studied for their functions in potato CIS. StAmy23 is localized in the cytoplasm, whereas StBAM1 and StBAM9 are targeted to the plastid stroma and starch granules, respectively. Genetic transformation of these amylases in potatoes by RNA interference showed that β-amylase activity could be decreased in cold-stored tubers by silencing of StBAM1 and collective silencing of StBAM1 and StBAM9. However, StBAM9 silencing did not decrease β-amylase activity. Silencing StBAM1 and StBAM9 caused starch accumulation and lower RS, which was more evident in simultaneously silenced lines, suggesting functional redundancy. Soluble starch content increased in RNAi-StBAM1 lines but decreased in RNAi-StBAM9 lines, suggesting that StBAM1 may regulate CIS by hydrolysing soluble starch and StBAM9 by directly acting on starch granules. Moreover, StBAM9 interacted with StBAM1 on the starch granules. StAmy23 silencing resulted in higher phytoglycogen and lower RS accumulation in cold-stored tubers, implying that StAmy23 regulates CIS by degrading cytosolic phytoglycogen. Our findings suggest that StAmy23, StBAM1, and StBAM9 function in potato CIS with varying levels of impact.
冷诱导增甜（CIS）会损害加工产品的质量。淀粉酶将淀粉转化为还原糖（RS）被认为是 CIS 的主要途径之一，但研究并不充分。研究了 StAmy23、StBAM1 和 StBAM9 这三种淀粉在 CIS 中的功能。StAmy23 定位于细胞质中，而 StBAM1 和 StBAM9 分别靶向质体基质和淀粉颗粒。通过 RNA 干扰对这些淀粉在马铃薯中的转化表明，通过沉默 StBAM1 和 StBAM1 和 StBAM9 的集体沉默，可以降低冷储存块茎中的β-淀粉酶活性。然而，沉默 StBAM9 并不能降低β-淀粉酶活性。沉默 StBAM1 和 StBAM9 导致淀粉积累和 RS 降低，在同时沉默的系中更为明显，表明功能冗余。在 RNAi-StBAM1 系中可溶性淀粉含量增加，但在 RNAi-StBAM9 系中减少，表明 StBAM1 可能通过水解可溶性淀粉，StBAM9 可能通过直接作用于淀粉颗粒来调节 CIS。此外，StBAM9 与淀粉颗粒上的 StBAM1 相互作用。沉默 StAmy23 导致冷储存块茎中植物糖含量升高和 RS 积累降低，表明 StAmy23 通过降解细胞质植物糖来调节 CIS。我们的研究结果表明，StAmy23、StBAM1 和 StBAM9 在 CIS 中具有不同程度的功能。
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