Root nodule symbiosis allows legumes to meet their nitrogen requirements. However, the causes of symbiosis failure at high temperatures remain unknown. We demonstrated that elevated temperatures affec...

Every cell must decide what enters the nucleus and what stays out. The nuclear pore complex (NPC), built from proteins called nucleoporins (NUPs), spans the double membrane of the nuclear envelope and shuttles molecules between the cytoplasm and the nucleus. Most NPC components serve this universal housekeeping role, so it was striking when a handful turned out to matter specifically for symbiosis. The NUP107-160 subcomplex, which forms the outer ring of the pore (Tamura et al. 2010), was first linked to symbiosis in the model legume Lotus japonicus. Mutants in 3 of its members, NUP133, NUP85, and NENA, show impaired root nodulation and arbuscular mycorrhization. These mutants also lack the nuclear calcium spiking triggered by host perception of symbiotic microbes (Kanamori et al. 2006; Saito et al. 2007; Groth et al. 2010). This calcium spiking requires nuclear envelope-localized cation channels, CASTOR and POLLUX, in Lotus (Charpentier et al. 2008). The same pathway operates in the related model legume Medicago truncatula, where the Pollux ortholog DMI1 fills this role (Ané et al. 2004). The function of these channels likely depends on reaching the inner nuclear membrane, but how these NUPs influence symbiotic signaling has remained unclear for nearly 2 decades.

The nuclear pore complex controls the movement of proteins into and out of the nucleus, allowing cells to regulate protein localization and abundance. This process influences how organisms respond to environmental stimuli. Components of the nuclear pore complex, including the NUP107-160 sub-complex, NUP133, NUP85, and NENA, are required for root nodulation and arbuscular mycorrhization in Lotus japonicus. However, the specific role of these nucleoporins in symbiotic signaling was poorly understood. Through reverse genetics, we discovered that NUP133 is also required for symbiosis in Medicago truncatula, although the mutant phenotypes were less pronounced than in Lotus. Overexpression of the symbiotic ion channels Medicago DMI1 and Lotus Castor and Pollux in the Lotus Ljnup133, Ljnup85, and Ljnena mutants partially alleviated the nodulation defects. Notably, in NUP107-160 sub-complex mutants of Lotus and Medicago, the accumulation of GFP-labeled Pollux and DMI1 on the inner nuclear membrane was reduced, indicating the NUP107-160 sub-complex plays a key role in regulating the distribution of DMI1 and Pollux on the nuclear envelope. This highlights the extreme sensitivity of nodulation in Lotus to changes in the abundance of Pollux on the inner nuclear membrane. In contrast, Medicago appears to exhibit greater tolerance to alterations in the distribution of DMI1 on the nuclear envelope.

She made key contributions to US cold-war science despite facing huge barriers as a Black woman.

Jean-Michel Ané