In this study, an cadmium (Cd)-immobilizing and arginine decarboxylase-producing endophytic Sphingomonas sp. strain C40 obtained from the seeds of Oryza sativa Cliangyou 513 was characterized for its Cd availability and Cd uptake in host rice using hydroponic and soil experiments. The Cd concentration decreased by 51–95% compared to the control, while the spermidine concentration increased by 19–25% with Cd compared with no Cd in the strain C40-inoculated solution. Strain C40 decreased the above-ground tissue Cd content by 27–37% and increased spermine and spermidine contents by 28–67% and the expression levels of genes involved in spermine and spermidine production by 29–217% in rice roots compared to the controls. Furthermore, correlation analyses showed the significantly negative correlation between rice root spermine and spermidine contents and above-ground tissue Cd content. In the Cd-added soil, strain C40 promoted the rice biomass by 29–36% and decreased rice root, above-ground tissue, and grain Cd contents by 18, 16, and 33% and total grain Cd uptake by 14% compared with the controls at the maturity stage. Strain C40 decreased the exchangeable Cd content by 27% and increased the Fe and Mn oxides-bound Cd content by 45% in the rice rhizosphere soils at the maturity stage compared with the controls. These results suggested that the endophytic bacterial strain C40 increased rice root polyamine production and their related gene expression and the transformation of available Cd to unavailable Cd, leading to reduced Cd accumulation and translocation from the rice roots to grains.

在这项研究中，固定化镉（Cd）和产生精氨酸脱羧酶的内生鞘氨醇单胞菌sp.。水稻种子获得的菌株C40利用水培和土壤实验，对两优513进行了表征，研究了寄主水稻中Cd的有效性和Cd的吸收。与对照相比，接种C40菌株的溶液中Cd的浓度与对照相比降低了51–95％，而亚精胺的浓度与Cd相比增加了19–25％。与对照相比，菌株C40使水稻根部的地上部分Cd含量降低了27-37％，并使精胺和亚精胺的含量增加了28-67％，参与精胺和亚精胺的基因的表达水平降低了29-217％。 。此外，相关分析表明，稻根精胺和亚精胺含量与地上组织Cd含量呈显着负相关。在添加Cd的土壤中，菌株C40使水稻生物量提高了29–36％，并减少了水稻根系，地上组织，与成熟期相比，Cd含量分别提高了18％，16％和33％，总Cd吸收量达到了14％。与对照相比，在根际成熟期，水稻根际土壤中的C40菌株使可交换Cd含量降低了27％，并使与Fe和Mn氧化物结合的Cd含量提高了45％。这些结果表明，内生细菌菌株C40增加了水稻根系多胺的产生及其相关基因的表达，以及有效Cd向不可用Cd的转化，从而降低了Cd的积累和从水稻根系向谷物的转运。与对照相比，在根际成熟期，水稻根际土壤中的C40菌株使可交换Cd含量降低了27％，并使与Fe和Mn氧化物结合的Cd含量提高了45％。这些结果表明，内生细菌菌株C40增加了水稻根系多胺的产生及其相关基因的表达，以及有效Cd向不可用Cd的转化，从而降低了Cd的积累和从水稻根系向谷物的转运。与对照相比，在根际成熟期，水稻根际土壤中的C40菌株使可交换Cd含量降低了27％，并使与Fe和Mn氧化物结合的Cd含量提高了45％。这些结果表明，内生细菌菌株C40增加了水稻根系多胺的产生及其相关基因的表达，以及有效Cd向不可用Cd的转化，从而降低了Cd的积累和从水稻根系向谷物的转运。