Endophytes have the potential to enhance the ability of plants to resist salt stress, improving crop development and yield. Therefore, in this study, we isolated an endophyte that produced large amounts of exopolysaccharides (EPSs) from the roots of sea rice and examined its effects on the physiological responses of rice (Oryza sativa L. ssp. japonica "Nipponbare") seedlings to salt stress using hydroponic experiments. The endophyte was named Pantoea alhagi NX-11 based on its morphological characteristics and 16S ribosomal DNA (rDNA) sequence alignment. Rice seedlings that had been inoculated with P. alhagi NX-11 exhibited a 30.3% increase in fresh weight, a 28.6% increase in root length, a 51.6% increase in shoot length, and a 26.3% increase in chlorophyll content compared with control seedlings under normal conditions. In addition, inoculated rice seedlings had a 37.5% lower malondialdehyde content, a 133% higher K+/Na+ ratio, and a 52.8% higher proline content after 7 days under salt stress, as well as up-regulated expression of proline synthase, down-regulated expression of proline dehydrogenase, and enhanced antioxidant enzyme activities. Interestingly, rice seedlings that were inoculated with an EPS-deficient strain named NX-11eps- that was obtained by atmospheric and room temperature plasma (ARTP) mutagenesis were damaged by salt stress and had similar physiological and biochemical indicators to the control group. Therefore, we speculate that the ability of P. alhagi NX-11 to enhance the salt tolerance of rice seedlings is related to the EPSs it produces.

中文翻译：

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内生菌泛菌NX-11通过分泌胞外多糖减轻盐胁迫对水稻幼苗的伤害。

内生植物具有增强植物抗盐胁迫能力，改善作物生长和产量的潜力。因此，在这项研究中，我们从海稻的根部分离出了产生大量胞外多糖（EPS）的内生菌，并研究了其对水稻（Oryza sativa L. ssp。japonica“ Nipponbare”）幼苗对盐分生理反应的影响。使用水培实验来缓解压力。内生植物因其形态特征和16S核糖体DNA（rDNA）序列比对而被命名为Pantoea alhagi NX-11。与对照幼苗相比，接种了P. alhagi NX-11的水稻幼苗的鲜重增加了30.3％，根长增加了28.6％，苗长增加了51.6％，叶绿素含量增加了26.3％在正常情况下。此外，盐胁迫7天后，接种的水稻幼苗的丙二醛含量降低了37.5％，K + / Na +比降低了133％，脯氨酸含量提高了52.8％，脯氨酸合酶的表达上调，而脯氨酸的表达下调。脯氨酸脱氢酶，增强抗氧化酶活性。有趣的是，接种了通过大气和室温血浆（ARTP）诱变获得的EPS缺陷菌株NX-11eps-的水稻幼苗受到盐胁迫的破坏，其生理和生化指标与对照组相似。因此，我们推测P. alhagi NX-11增强水稻幼苗耐盐性的能力与其产生的EPS有关。盐胁迫下7天后，脯氨酸含量增加8％，脯氨酸合酶表达上调，脯氨酸脱氢酶表达下调，抗氧化酶活性增强。有趣的是，接种了通过大气和室温血浆（ARTP）诱变获得的EPS缺陷菌株NX-11eps-的水稻幼苗受到盐胁迫的破坏，其生理和生化指标与对照组相似。因此，我们推测P. alhagi NX-11增强水稻幼苗耐盐性的能力与其产生的EPS有关。盐胁迫下7天后脯氨酸含量增加8％，脯氨酸合酶表达上调，脯氨酸脱氢酶表达下调，抗氧化酶活性增强。有趣的是，接种了通过大气和室温血浆（ARTP）诱变获得的EPS缺陷菌株NX-11eps-的水稻幼苗受到盐胁迫的破坏，其生理和生化指标与对照组相似。因此，我们推测P. alhagi NX-11增强水稻幼苗耐盐性的能力与其产生的EPS有关。通过大气和室温血浆（ARTP）诱变获得的EPS缺陷菌株NX-11eps-接种的水稻幼苗受到盐胁迫的破坏，其生理和生化指标与对照组相似。因此，我们推测P. alhagi NX-11增强水稻幼苗耐盐性的能力与其产生的EPS有关。通过大气和室温血浆（ARTP）诱变获得的EPS缺陷菌株NX-11eps-接种的水稻幼苗受到盐胁迫的破坏，其生理和生化指标与对照组相似。因此，我们推测P. alhagi NX-11增强水稻幼苗耐盐性的能力与其产生的EPS有关。