BACKGROUND Plant genomes contain a large number of HAK/KUP/KT transporters, which play important roles in potassium uptake and translocation, osmotic potential regulation, salt tolerance, root morphogenesis and plant development. Potassium deficiency in the soil of a sugarcane planting area is serious. However, the HAK/KUP/KT gene family remains to be characterized in sugarcane (Saccharum). RESULTS In this study, 30 HAK/KUP/KT genes were identified in Saccharum spontaneum. Phylogenetics, duplication events, gene structures and expression patterns were analyzed. Phylogenetic analysis of the HAK/KUP/KT genes from 15 representative plants showed that this gene family is divided into four groups (clades I-IV). Both ancient whole-genome duplication (WGD) and recent gene duplication contributed to the expansion of the HAK/KUP/KT gene family. Nonsynonymous to synonymous substitution ratio (Ka/Ks) analysis showed that purifying selection was the main force driving the evolution of HAK/KUP/KT genes. The divergence time of the HAK/KUP/KT gene family was estimated to range from 134.8 to 233.7 Mya based on Ks analysis, suggesting that it is an ancient gene family in plants. Gene structure analysis showed that the HAK/KUP/KT genes were accompanied by intron gain/loss in the process of evolution. RNA-seq data analysis demonstrated that the HAK/KUP/KT genes from clades II and III were mainly constitutively expressed in various tissues, while most genes from clades I and IV had no or very low expression in the tested tissues at different developmental stages. The expression of SsHAK1 and SsHAK21 was upregulated in response to low-K+ stress. Yeast functional complementation analysis revealed that SsHAK1 and SsHAK21 could rescue K+ uptake in a yeast mutant. CONCLUSIONS This study provided insights into the evolutionary history of HAK/KUP/KT genes. HAK7/9/18 were mainly expressed in the upper photosynthetic zone and mature zone of the stem. HAK7/9/18/25 were regulated by sunlight. SsHAK1 and SsHAK21 played important roles in mediating potassium acquisition under limited K+ supply. Our results provide valuable information and key candidate genes for further studies on the function of HAK/KUP/KT genes in Saccharum.

中文翻译：

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HAK / KUP / KT基因家族的全基因组系统表征及其在植物生长过程中以及响应蔗糖中低K +胁迫的表达特征。

背景技术植物基因组包含大量的HAK / KUP / KT转运蛋白，其在钾的吸收和转运，渗透势调节，盐耐性，根形态发生和植物发育中起重要作用。甘蔗种植区土壤钾缺乏严重。但是，HAK / KUP / KT基因家族仍有待在甘蔗（蔗糖）中鉴定。结果在这项研究中，自发性酿酒酵母中鉴定出30个HAK / KUP / KT基因。系统发育，重复事件，基因结构和表达模式进行了分析。对来自15个代表性植物的HAK / KUP / KT基因进行系统发育分析表明，该基因家族分为四类（第I-IV类）。古老的全基因组重复（WGD）和最近的基因重复都促进了HAK / KUP / KT基因家族的扩展。非同义替代比（Ka / Ks）分析表明，纯化选择是驱动HAK / KUP / KT基因进化的主要动力。根据Ks分析，HAK / KUP / KT基因家族的发散时间估计为134.8至233.7 Mya，表明它是植物中的古老基因家族。基因结构分析表明，HAK / KUP / KT基因在进化过程中伴随着内含子的增减。RNA-seq数据分析表明，进化支II和III的HAK / KUP / KT基因主要在各种组织中组成性表达，而进化支I和IV的大多数基因在不同发育阶段的受试组织中均没有表达或表达很低。SsHAK1和SsHAK21的表达上调响应低K +压力。酵母功能互补分析表明，SsHAK1和SsHAK21可以挽救酵母突变体中的K +吸收。结论这项研究提供了对HAK / KUP / KT基因进化史的见解。HAK7 / 9/18主要在茎的上部光合区和成熟区表达。HAK7 / 9/18/25受阳光调节。在钾离子供应有限的情况下，SsHAK1和SsHAK21在介导钾的吸收中起着重要作用。我们的结果提供了宝贵的信息和关键的候选基因，以进一步研究蔗糖中HAK / KUP / KT基因的功能。HAK7 / 9/18/25受阳光调节。在钾离子供应有限的情况下，SsHAK1和SsHAK21在介导钾的吸收中起着重要作用。我们的结果提供了宝贵的信息和关键的候选基因，以进一步研究蔗糖中HAK / KUP / KT基因的功能。HAK7 / 9/18/25受阳光调节。在钾离子供应有限的情况下，SsHAK1和SsHAK21在介导钾的吸收中起着重要作用。我们的结果提供了宝贵的信息和关键的候选基因，以进一步研究蔗糖中HAK / KUP / KT基因的功能。