Joint International Research Laboratory of Water and Nutrient in Crops, Haixia Institute of Ecology and Environmental Engineering, College of Resource and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
College of Agriculture, Yangzhou University, Yangzhou 225009, China.
Plant Physiol. 2022 Nov 28;190(4):2449-2465. doi: 10.1093/plphys/kiac418.
The rhizosheath is a belowground area that acts as a communication hub at the root-soil interface to promote water and nutrient acquisition. Certain crops, such as white lupin (Lupinus albus), acquire large amounts of phosphorus (P), owing partially to exudation of acid phosphatases (APases). Plant growth-promoting rhizobacteria also increase soil P availability. However, potential synergistic effects of root APases and rhizosheath-associated microbiota on P acquisition require further research. In this study, we investigated the roles of root purple APases (PAPs) and plant growth-promoting rhizobacteria in rhizosheath formation and P acquisition under conditions of soil drying (SD) and P treatment (+P: soil with P fertilizer; -P: soil without fertilizer). We expressed purple acid phosphatase12 (LaPAP12) in white lupin and rice (Oryza sativa) plants and analyzed the rhizosheath-associated microbiome. Increased or heterologous LaPAP12 expression promoted APase activity and rhizosheath formation, resulting in increased P acquisition mainly under SD-P conditions. It also increased the abundance of members of the genus Bacillus in the rhizosheath-associated microbial communities of white lupin and rice. We isolated a phosphate-solubilizing, auxin-producing Bacillus megaterium strain from the rhizosheath of white lupin and used this to inoculate white lupin and rice plants. Inoculation promoted rhizosheath formation and P acquisition, especially in plants with increased LaPAP12 expression and under SD-P conditions, suggesting a functional role of the bacteria in alleviating P deficit stress via rhizosheath formation. Together, our results suggest a synergistic enhancing effect of LaPAP12 and plant growth-promoting rhizobacteria on rhizosheath formation and P acquisition under SD-P conditions.
根鞘是地下区域，作为根-土界面的通讯枢纽，促进水和养分的获取。某些作物，如白 Lupinus albus，会大量吸收磷（P），部分原因是酸性磷酸酶（APases）的分泌。植物促生根际细菌也会增加土壤 P 的有效性。然而，根 APases 和根鞘相关微生物区系对 P 吸收的潜在协同作用需要进一步研究。在这项研究中，我们研究了根紫色 APases（PAPs）和植物促生根际细菌在土壤干燥（SD）和 P 处理（+P：施磷肥土壤；-P：无肥土壤）条件下对根鞘形成和 P 吸收的作用。我们在白 Lupinus 和水稻（Oryza sativa）植物中表达了紫色酸性磷酸酶 12（LaPAP12），并分析了根鞘相关微生物组。增加或异源 LaPAP12 表达促进了 APase 活性和根鞘形成，主要在 SD-P 条件下增加了 P 的吸收。它还增加了 Bacillus 属成员在白 Lupinus 和水稻根鞘相关微生物群落中的丰度。我们从白 Lupinus 的根鞘中分离出了一株溶磷产生长素的巨大芽孢杆菌菌株，并将其接种到白 Lupinus 和水稻植株上。接种促进了根鞘的形成和 P 的吸收，特别是在 LaPAP12 表达增加和 SD-P 条件下的植物中，这表明细菌通过根鞘的形成在缓解 P 缺乏胁迫方面发挥了功能作用。总之，我们的研究结果表明，LaPAP12 和植物促生根际细菌在 SD-P 条件下对根鞘形成和 P 吸收具有协同增强作用。
