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

光对豆科植物和根瘤菌之间能量昂贵的固氮共生提供碳至关重要。在本研究中，我发现光敏色素B（phyB）是监测系统的一部分，用于检测次优光照条件，这通常会抑制接种中根瘤菌后日本莲节的发育。我发现，与野生型MG20相比，L. japonicus phyB突变体产生的根瘤数量明显减少。为了探索除光同化产生外的其他原因，通过嫁接试验研究了根基因型发生局部控制的可能性。结果表明，根瘤的形成是由茎部基因型而不是根基因型决定的。为了探索除光同化外的系统控制机制，我们将野生型MG20植物从白光转移到低或高红/远红（FR）光比不同的条件下。在低R/ FR光照下，尽管光同化物含量较高，但与高R/ FR光照下生长的植株相比，m20根瘤的数量显著减少。此外，在低R/ FR光照下生长的野生型植株和白光下生长的phyB突变体植株中，茉莉酸（jasmonic acid， JA）应答基因的表达减少，这与phyB突变体中JA- ile含量降低有关。此外，JA处理对低海拔野生型植株侵染线的形成和根瘤的形成均有正向影响

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