Institute of Crop Science (NICS), National Agriculture and Food Research Organization, 2-1-2, Kannondai, Tsukuba, Ibaraki, 305-8518, Japan.
Faculty of Agriculture, Shinshu University, 8304 Minami-minowa, Nagano, 399-4598, Japan.
BMC Plant Biol. 2018 Jan 3;18(1):2. doi: 10.1186/s12870-017-1218-9.
Sorghum (Sorghum bicolor L.) is used as a raw material for biofuels because it accumulates sugars at high levels in the stem. Lodging of sorghum occurs when the soil is wet and very high winds blow across the field. In root lodging, the roots are pulled loose from the soil, causing the plant to fall over. Lodging reduces the yield of nonstructural carbohydrates. It is not yet clear which genes show changes in expression when sorghum falls over. We compared whole-gene expression in the mature stems of intact and lodged sorghum plants, with a focus on comparisons from the perspective of differences in sugar accumulation or degradation.
Lodging decreased sucrose content, starch content, and ratio of sucrose to total sugars in the stems of the sorghum cultivar SIL-05. Particular paralogs of SWEET and TMT family genes, which encode sucrose or hexose transporters, or both, were significantly highly expressed in intact or lodged sorghum stems. In intact stems, genes encoding the glucose-6-phosphate translocator, aquaporins, and enzymes involved in photosynthesis and starch synthesis were highly expressed. In lodged sorghum stems, expression of genes associated with sucrose or starch degradation or energy production was increased. Notably, expression of genes encoding enzymes catalyzing irreversible reactions and associated with the first steps of these metabolic pathways (e.g. INV, SUS, and hexokinase- and fructokinase-encoding genes) was significantly increased by lodging. Expression of SUT, SPS, and SPP was almost the same in intact and lodged sorghum.
Specific paralogs of sucrose-associated genes involved in metabolic pathways and in membrane transport were expressed in the stems of sorghum SIL-05 at the full-ripe stage. Root lodging drastically changed the expression of these genes from sucrose accumulation to degradation. The changes in gene expression resulted in decreases in sugar content and in the proportion of sucrose to hexoses in the stems of lodged plants.
高粱（Sorghum bicolor L.）因其在茎中高水平积累糖而被用作生物燃料的原料。高粱倒伏发生在土壤湿润且强风刮过田地时。在根倒伏中，根系从土壤中松动，导致植物倒伏。倒伏降低了非结构性碳水化合物的产量。目前尚不清楚高粱倒伏时哪些基因的表达发生变化。我们比较了完整和倒伏高粱植株成熟茎中的全基因表达，重点比较了糖积累或降解差异的角度。
倒伏降低了高粱品种 SIL-05 茎中的蔗糖含量、淀粉含量和蔗糖与总糖的比例。蔗糖或己糖转运蛋白或两者的特定 SWEET 和 TMT 家族基因的特定等位基因在完整或倒伏的高粱茎中表达显著上调。在完整的茎中，编码葡萄糖-6-磷酸转运蛋白、水通道蛋白以及参与光合作用和淀粉合成的酶的基因高度表达。在倒伏的高粱茎中，与蔗糖或淀粉降解或能量产生相关的基因表达增加。值得注意的是，编码催化不可逆反应的酶的基因表达与这些代谢途径的第一步（例如 INV、SUS 和编码己糖激酶和果糖激酶的基因）相关，倒伏显著增加。SUT、SPS 和 SPP 在完整和倒伏的高粱中的表达几乎相同。
在成熟的高粱 SIL-05 茎中，参与代谢途径和膜转运的蔗糖相关基因的特定等位基因表达。根倒伏从蔗糖积累到降解剧烈改变了这些基因的表达。基因表达的变化导致糖含量和倒伏植物茎中蔗糖与己糖比例降低。
