Bizzarri Marco, Delledonne Massimo, Ferrarini Alberto, Tononi Paola, Zago Elisa, Vittori Doriano, Damiani Francesco, Paolocci Francesco
Department of Science and Technology for Agriculture, Forests, Nature and Energy (DAFNE), University of Tuscia, Viterbo, Italy.
Department of Biotechnology, University of Verona, Verona, Italy.
Front Plant Sci. 2020 Feb 21;11:101. doi: 10.3389/fpls.2020.00101. eCollection 2020.
L., known as the Jerusalem artichoke, is a hexaploid plant species, adapted to low-nutrient soils, that accumulates high levels of inulin in its tubers. Inulin is a fructose-based polysaccharide used either as dietary fiber or for the production of bioethanol. Key enzymes involved in inulin biosynthesis are well known. However, the gene networks underpinning tuber development and inulin accumulation in remain elusive. To fill this gap, we selected 6,365 expressed sequence tags (ESTs) from an library to set up a microarray platform and record their expression across three tuber developmental stages, when rhizomes start enlarging (T), at maximum tuber elongation rate (T), and at tuber physiological maturity (T), in "VR" and "K8-HS142"clones. The former was selected as an early tuberizing and the latter as a late-tuberizing clone. We quantified inulin and starch levels, and qRT-PCR confirmed the expression of critical genes accounting for inulin biosynthesis. The microarray analysis revealed that the differences in morphological and physiological traits between tubers of the two clones are genetically determined since T and that is relatively low the number of differentially expressed ESTs across the stages shared between the clones (93). The expression of ESTs for () and (), the two critical genes for fructans polymerization, resulted to be temporarily synchronized and mirror the progress of inulin accumulation and stretching. The expression of ESTs for starch biosynthesis was insignificant throughout the developmental stages of the clones in line with the negligible level of starch into their mature tubers, where inulin was the dominant polysaccharide. Overall, our study disclosed candidate genes underpinning the development and storage of carbohydrates in the tubers of two clones. A model according to which the steady-state levels of and transcripts are developmentally controlled and might represent a limiting factor for inulin accumulation has been provided. Our finding may have significant repercussions for breeding clones with improved levels of inulin for food and chemical industry.
菊芋（Helianthus tuberosus L.），又称洋姜，是一种六倍体植物物种，适应低营养土壤，其块茎中积累高水平的菊粉。菊粉是一种基于果糖的多糖，用作膳食纤维或用于生产生物乙醇。参与菊粉生物合成的关键酶是众所周知的。然而，支撑菊芋块茎发育和菊粉积累的基因网络仍然难以捉摸。为了填补这一空白，我们从菊芋文库中选择了6365个表达序列标签（EST），建立了一个微阵列平台，并记录它们在“VR”和“K8-HS142”克隆的三个块茎发育阶段的表达情况，这三个阶段分别是根茎开始膨大时（T1）、块茎伸长率最高时（T2）和块茎生理成熟时（T3）。前者被选为早期结薯克隆，后者被选为晚期结薯克隆。我们对菊粉和淀粉水平进行了定量，qRT-PCR证实了参与菊粉生物合成的关键基因的表达。微阵列分析表明，两个克隆块茎在形态和生理特征上的差异是由基因决定的，因为在T1阶段，两个克隆之间共享的不同表达EST的数量相对较少（93个）。参与果聚糖聚合的两个关键基因蔗糖：蔗糖1 - 果糖基转移酶（1 - SST）和1 - 果聚糖：果聚糖1 - 果糖基转移酶（1 - FF T）的EST表达在T2阶段暂时同步，并反映了菊粉积累和延伸的进程。在克隆的整个发育阶段，淀粉生物合成的EST表达不显著，这与它们成熟块茎中淀粉含量可忽略不计一致，其中菊粉是主要的多糖。总体而言，我们的研究揭示了支撑两个菊芋克隆块茎中碳水化合物发育和储存的候选基因。我们提供了一个模型，根据该模型，1 - SST和1 - FF T转录本的稳态水平受到发育调控，可能是菊粉积累的限制因素。我们的发现可能对培育菊粉含量更高的克隆用于食品和化学工业产生重大影响。
