Forestry College, Fujian Agriculture and Forestry University, Fuzhou, 350002, Fujian, China.
Chinese Fir Engineering and Technological Research Center, National Forestry and Grassland Administration, Fuzhou, 350002, Fujian, China.
BMC Plant Biol. 2021 Nov 10;21(1):525. doi: 10.1186/s12870-021-03245-6.
Phosphorus is one of the essential elements for plant growth and development, but available phosphorus (Pi) content in many soil types is low. As a fast-growing tree species for timber production, Chinese fir is in great demand of Pi, and the lack of Pi in soil restricts the increase of productivity of Chinese fir plantation. Root morphology and the synthesis and secretion of organic acids play an important role in the uptake of phosphorus, but the molecular mechanisms of Chinese fir root responses to Pi deficiency are largely unexplored. In this study, seedlings of Yang 061 clone were grown under three Pi supply levels (0, 5 and 10 mg·L-1 P) and morphological attributes, organic acid content and enzyme activity were measured. The transcriptome data of Chinese fir root system were obtained and the expression levels of phosphorus responsive genes and organic acid synthesis related genes on citric acid and glyoxylate cycle pathway were determined.
We annotated 50,808 Unigenes from the transcriptome of Chinese fir roots. Among differentially expressed genes, seven genes of phosphate transporter family and 17 genes of purple acid phosphatase family were up-regulated by Pi deficiency, two proteins of SPX domain were up-regulated and one was down-regulated. The metabolic pathways of the citric acid and glyoxylate cycle pathway were mapped, and the expression characteristics of the related Unigenes under different phosphorus treatments were analyzed. The genes involved in malic acid and citric acid synthesis were up-regulated, and the activities of the related enzymes were significantly enhanced under long-term Pi stress. The contents of citric acid and malic acid in the roots of Chinese fir increased after 30 days of Pi deficiency.
Chinese fir roots showed increased expression of genes related with phosphorus starvation, citrate and malate synthesis genes, increased content of organic acids, and enhanced activities of related enzymes under Pi deficiency. The results provide a new insight for revealing the molecular mechanism of adaption to Pi deficiency and the pathway of organic acid synthesis in Chinese fir roots.
磷是植物生长和发育所必需的元素之一，但许多土壤类型中的有效磷（Pi）含量较低。作为一种用于木材生产的快速生长树种，杉木对 Pi 的需求量很大，而土壤中 Pi 的缺乏限制了杉木人工林生产力的提高。根系形态以及有机酸的合成和分泌在磷的吸收中起着重要作用，但杉木根系对 Pi 缺乏的响应的分子机制在很大程度上尚未被探索。在这项研究中，在三种 Pi 供应水平（0、5 和 10 mg·L-1 P）下培养了杨 061 无性系的幼苗，并测量了形态特征、有机酸含量和酶活性。获得了杉木根系的转录组数据，并确定了磷响应基因和柠檬酸和乙醛酸循环途径中有机酸合成相关基因的表达水平。
我们从杉木根系的转录组中注释了 50808 个 Unigenes。在差异表达基因中，磷酸盐转运蛋白家族的七个基因和紫色酸性磷酸酶家族的十七个基因被 Pi 缺乏所上调，两个 SPX 结构域的蛋白质被上调，一个被下调。柠檬酸和乙醛酸循环途径的代谢途径被映射，并且在不同磷处理下相关 Unigenes 的表达特征被分析。参与苹果酸和柠檬酸合成的基因被上调，并且在长期 Pi 胁迫下，相关酶的活性显著增强。在 Pi 缺乏 30 天后，杉木根中的柠檬酸和苹果酸含量增加。
在 Pi 缺乏下，杉木根表现出与磷饥饿、柠檬酸和苹果酸合成基因相关的基因表达增加，有机酸含量增加，相关酶的活性增强。研究结果为揭示杉木根系适应 Pi 缺乏的分子机制和有机酸合成途径提供了新的见解。
