Root nodulation is controlled by sensing the R/ FR ratio through phytochrome signaling

光对于为豆科植物和根瘤菌之间能量昂贵的固氮共生体提供碳至关重要。在这项研究中，我表明，光敏色素B（phyB）是监测系统的一部分，以检测次最佳的光照条件，通常抑制百脉根根瘤菌接种后的发展。我发现L.与野生型MG 20相比，MyphyB突变体显著减少。为了探讨光合产物产生以外的原因，通过嫁接实验研究了根基因型局部控制的可能性。结果表明，根瘤形成的基因型是地上部基因型，而不是根部基因型。为了探索排除光同化作用的系统控制机制，我们将野生型MG 20植物从白色光转移到低或高红光（R）/远红光（FR）比率不同的条件下。在低R/ FR光，MG 20根瘤的数量显着下降相比，植物生长在高R/ FR，即使光合产物含量较高的植物生长在低R/FR。此外，茉莉酸（JA）响应基因的表达下降，在低R/ FR光生长的野生型和白色光生长的phyB突变体植物，并与减少JA-Ile含量的phyB突变体。此外，JA处理对生长在低温下的野生型植物的侵染线形成和根瘤形成都有积极的影响。

Light is critical for supplying carbon to the energetically expensive, nitrogen-fixing symbiosis between legumes and rhizobia. In this study, I show that Phytochrome B(phyB) is part of the monitoring system to detect suboptimal light conditions, which normally suppress Lotus japonicus nodule development following Mesorhizobium loti inoculation. I found that the number of nodules produced by L. japonicus phyB mutants is significantly reduced compared to that of wild-type MG20. To explore causes other than photoassimilate production, the possibility that local control by the root genotype occurred was investigated by grafting experiments. The results showed that the shoot and not the root genotype is responsible for root nodule formation. To explore systemic control mechanisms exclusive of photoassimilation, we moved wild-type MG20 plants from white light to conditions that differed in their ratios of low or high red(R)/ far-red(FR) light. In low R/ FR light, the number of MG20 root nodules dramatically decreased compared to plants grown in high R/ FR even though photoassimilate content was higher for plants grown under low R/ FR. Also, the expression of jasmonic acid(JA)-responsive genes decreased in both low R/ FR light-grown wild-type and in white light-grown phyB mutant plants, and correlated with decreased JA-Ile content in the phyB mutant. Moreover, both infection thread formation and root nodule formation were positively influenced by JA treatment of wild-type plants grown in low