Many plants interact symbiotically with arbuscular mycorrhizal fungi to enhance inorganic phosphorus uptake, and legumes also develop a nodule symbiosis with rhizobia for nitrogen acquisition. The establishment and functioning of both symbioses rely on a common plant signaling pathway activated by structurally related Myc and Nod factors. Recently, a SPARK receptor-like kinase (RLK)/receptor-like cytoplasmic kinase (RLCK) complex was shown to be essential for arbuscular mycorrhiza formation in both monocot and dicot plants. Here, we show that in Aeschynomene legumes, the RLCK component of this receptor complex has undergone a gene duplication event and mediates a unique nodule symbiosis that is independent of rhizobial Nod factors. In Aeschynomene evenia, AeRLCK2 is crucial for nodule initiation but not for arbuscular mycorrhiza symbiosis. Additionally, AeRLCK2 physically interacts with and is phosphorylated by the cysteine-rich RLK, AeCRK, which is also required for nodulation. This finding uncovers an important molecular mechanism that controls the establishment of nodulation and is associated with Nod-independent symbiosis.

Nitrogen-fixing root nodule symbiosis (RNS) occurs in some eudicots, including legumes, and is regulated by the transcription factor NODULE INCEPTION (NIN), derived from the NIN-LIKE PROTEIN (NLP) family. However, how the NIN protein acquired RNS-specific functions remains unclear. We identify a previously undescribed motif in Lotus japonicus NIN, located downstream of the RWP-RK domain, which we term the FR. This motif broadens the DNA-binding specificity of NIN by stabilizing the RWP-RK dimer interface. nin mutants lacking the FR motif show defective nodulation and impaired nitrogen fixation. Arabidopsis NLP2 carries a NIN-type FR and shares key features with NIN. Furthermore, the NIN-type FR likely originated as early as gymnosperms, suggesting that the molecular feature of NIN for RNS regulation was inherited from ancestral NLPs before RNS emerged.

Evolutionary histories of effector proteins secreted by fungal pathogens to mediate plant colonization remain largely elusive. While most functionally characterized effectors modulate plant immunity, ...

Salicylic acid (SA) is a key plant hormone required for establishing resistance to many pathogens. SA biosynthesis involves two main metabolic pathways with multiple steps: the isochorismate and the p...

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Aphids hijack plant immunity via p-bodies, but plants fight back with a heat shock protein in an unexpected twist on defense.

The Ralstonia solanacearum effector PopP2 is a YopJ family acetyltransferase. PopP2 is known to dampen basal immune responses by acetylating defensive WRKY transcription factors, and probably by targ...