Hu Shuting, Song Linjin, Yi Xiaoping, Ni Xinyu, Cui Xiaoshuang, Duan Shaoqi, Jiang Rui, Lyu Dianqiu, Wang Jichun, Hu Baigeng, Liu Xun
Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, Chongqing, 400715, P.R. China.
Chongqing Key Laboratory of Biology and Genetic Breeding for Tuber and Root Crops, Southwest University, Chongqing, 400715, P.R. China.
Plant J. 2025 May;122(4):e70206. doi: 10.1111/tpj.70206.
The enzymes of STARCH SYNTHASE (SS) are key players in starch biosynthesis which have proven their impact on different aspects of the starch biosynthesis and functionalities. These SSs seem to be key differences among species and organs regarding their contributions to starch synthesis. The function of StSS5 in starch synthesis of tubers was proposed, but it remains to be investigated. Here, we generated two heterozygous biallelic mutants within the 5'-untranslated region of StSS5, which resulted in the knockdown of StSS5 in a dihaploid potato AC142 through the CRISPR/Cas9 system. We investigated the role of StSS5 in potato, which has a distinct pattern of granule initiation between leaf chloroplasts and tuber amyloplasts. The ss5 mutants produce fewer starch granules in chloroplasts and attenuate starch degradation during night periods in leaves. By contrast, the ss5 mutations induce supernumerary starch granule initiations, leading to the formation of compound starch granules in amyloplasts and a relatively higher amounts of small starch granules in tubers. Additionally, these distinct starch granule initiations in the ss5 mutants were associated with a decrease in tuber fresh weight and starch accumulation. Overall, our work demonstrates that StSS5 is critical for granule initiation in tuber amyloplasts and leaf chloroplasts of potato to modulate tuber development and starch accumulation, which may provide a strategy to improve tuber starch yield and modify starch properties of potato.
淀粉合酶（SS）的酶是淀粉生物合成中的关键参与者，已证明它们对淀粉生物合成和功能的不同方面有影响。这些SS在物种和器官对淀粉合成的贡献方面似乎存在关键差异。有人提出了StSS5在块茎淀粉合成中的功能，但仍有待研究。在这里，我们在StSS5的5'非翻译区内产生了两个杂合双等位基因突变体，通过CRISPR/Cas9系统导致双单倍体马铃薯AC142中StSS5的敲低。我们研究了StSS5在马铃薯中的作用，马铃薯在叶叶绿体和块茎造粉体之间具有独特的颗粒起始模式。ss5突变体在叶绿体中产生的淀粉颗粒较少，并在叶片夜间减弱淀粉降解。相比之下，ss5突变诱导了过多的淀粉颗粒起始，导致造粉体中复合淀粉颗粒的形成以及块茎中相对较多的小淀粉颗粒。此外，ss5突变体中这些独特的淀粉颗粒起始与块茎鲜重和淀粉积累的减少有关。总体而言，我们的工作表明，StSS5对于马铃薯块茎造粉体和叶叶绿体中的颗粒起始至关重要，以调节块茎发育和淀粉积累，这可能为提高块茎淀粉产量和改变马铃薯淀粉特性提供一种策略。
