Departamento de Botânica IB, USP, São Paulo, SP, 05508-090, Brazil.
BMC Plant Biol. 2021 Jan 7;21(1):23. doi: 10.1186/s12870-020-02795-5.
Sugarcane is capable to store large amounts of sucrose in the culm at maturity hence it became a major source of sucrose for the food and the renewable energy industries. Sucrose, the main disaccharide produced by photosynthesis, is mainly stored in the vacuole of the cells of non-photosynthetic tissues. Two pathways are known to release free sucrose in plant cells, one is de novo synthesis dependent on sucrose phosphate synthase (SPS) and sucrose phosphate phosphatase (S6PP) while the other is regulatory and dependent on sucrose synthase (SuSy) activity. The molecular understanding of genes that give rise to the expression of the enzyme sucrose phosphate phosphatase, responsible for the release of sucrose in the last synthetic step lag behind the regulatory SuSy gene.
Sugarcane genome sequencing effort disclosed the existence of a tandem duplication and the present work further support that both S6PP.1 and S6PP_2D isoforms are actively transcribed in young sugarcane plants but significantly less at maturity. Two commercial hybrids (SP80-3280 and R570) and both Saccharum spontaneum (IN84-58) and S.officinarum (BADILLA) exhibit transcriptional activity at three-month-old plants of the tandem S6PP_2D in leaves, culm, meristem and root system with a cultivar-specific distribution. Moreover, this tandem duplication is shared with other grasses and is ancestral in the group.
Detection of a new isoform of S6PP resulting from the translation of 14 exon-containing transcript (S6PP_2D) will contribute to the knowledge of sucrose metabolism in plants. In addition, expression varies along plant development and between sugarcane cultivars and parental species.
甘蔗在成熟时能够在茎中储存大量的蔗糖，因此成为食品和可再生能源行业蔗糖的主要来源。蔗糖是光合作用产生的主要二糖，主要储存在非光合组织细胞的液泡中。植物细胞中释放游离蔗糖有两种已知途径，一种是依赖蔗糖磷酸合酶（SPS）和蔗糖磷酸磷酸酶（S6PP）的从头合成途径，另一种是依赖蔗糖合酶（SuSy）活性的调节途径。负责蔗糖最后合成步骤释放的蔗糖磷酸磷酸酶基因的表达导致的分子理解落后于调节 SuSy 基因。
甘蔗基因组测序工作揭示了串联重复的存在，目前的工作进一步支持 S6PP.1 和 S6PP_2D 同工型在幼龄甘蔗植物中均有转录活性，但在成熟时显著减少。两个商业杂种（SP80-3280 和 R570）以及两个野生种（IN84-58 和 BADILLA）在三个月龄的植物叶片、茎、分生组织和根系中表现出串联 S6PP_2D 的转录活性，具有特定于品种的分布。此外，这种串联重复在其他禾本科植物中共享，是该组的祖先。
检测到 S6PP 的新同工型，这是由含有 14 个外显子的转录物（S6PP_2D）翻译而来，将有助于了解植物中的蔗糖代谢。此外，表达随植物发育和甘蔗品种以及亲本种间而变化。
