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During root nodule symbiosis, intracellular accommodation of rhizobia by legumes is a prerequisite for nitrogen fixation. For many legumes, rhizobial colonization initiates in root hairs through transcellular infection threads. In Medicago truncatula, VAPYRIN (VPY) and a putative E3 ligase LUMPY INFECTIONS (LIN) are required for infection thread development but their cellular and molecular roles are obscure. Here we show that LIN and its homolog LIN-LIKE interact with VPY and VPY-LIKE in a subcellular complex localized to puncta both at the tip of the growing infection thread and at the nuclear periphery in root hairs and that the punctate accumulation of VPY is positively regulated by LIN. We also show that an otherwise nuclear and cytoplasmic exocyst subunit, EXO70H4, systematically co-localizes with VPY and LIN during rhizobial infection. Genetic analysis shows that defective rhizobial infection in exo70h4 is similar to that in vpy and lin. Our results indicate that VPY, LIN and EXO70H4 are part of the symbiosis-specific machinery required for polar growth of infection threads., Many legumes accommodate rhizobial symbionts via transcellular infection threads. Here the authors show that in Medicago root hairs, polar growth of the infection thread requires a tip-localized protein complex consisting of VPY and VPY-like proteins that are stabilized by the E3 ligase LIN, as well as an exocyst complex subunit.

Miaoxia Liu,1,2,* Ruihong Wu,1,3,* Xu Liu,1 Hongqin Xu,1 Xiumei Chi,1,3 Xiaomei Wang,1 Mengru Zhan,1 Bao Wang,1 Fei Peng,1 Xiuzhu Gao,1,3 Ying Shi,1 Xiaoyu Wen,1 Yali Ji,2 Qinglong Jin,1 Junqi Niu1 1Department of Hepatology, First Hospital of Jilin University, Changchun, Jilin Province 130021, People’s Republic of China; 2Hepatology Unit, Department of Infectious Diseases, Nanfang Hospital, Southern Medical University, Guangzhou 510515, People’s Republic of China; 3Phase I Clinical Research Center, First Hospital of Jilin University, Changchun, Jilin Province 130021, People’s Republic of China*These authors contributed equally to this workCorrespondence: Qinglong JinDepartment of Hepatology, First Hospital of Jilin University, 71 Xin Min Street, Changchun 130021, People’s Republic of ChinaTel/Fax +86-431-81875103Email jinql2016@163.comPurpose: GALAD is a statistical model for estimating the likelihood of having hepatocellular carcinoma (HCC) based on gender, age, AFP, AFP-L3, and PIVKA-II. We aimed to assess its performance and build new models in China, where hepatitis B virus (HBV) is the leading etiology of HCC.Patients and Methods: We built the GALAD-C model with the same five variables in GALAD, and the GAAP model with gender, age, AFP, and PIVKA-II, using logistic regression based on 242 patients with HCC and 283 patients with chronic liver disease (CLD). We also collected 50 patients with other malignant liver tumors (OMTs) and 50 healthy controls (HCs). A test dataset (169 patients with HCC and 139 with CLD) was used to test the performance of GAAP.Results: The GALAD-C and GAAP models achieved comparable performance (area under the receiver operating characteristic curve [AUC], 0.922 vs 0.914), and both were superior to GALAD, PIVKA-II, AFP, and AFP-L3% (AUCs, 0.891, 0.869, 0.750, and 0.711) for discrimination of HCC from CLD for the entire dataset. The AUCs of the GALAD, GALAD-C and GAAP models were excellent for the hepatitis C virus (HCV) subgroup (0.939, 0.958 and 0.954), and for discrimination HCC from HCs (0.988, 0.982, and 0.979), but were relatively lower for the HBV subgroup (0.855, 0.904, and 0.894), and for HCC within Milan Criteria (0.810, 0.841, and 0.840). They were not superior to AFP (0.873) for discrimination of HCC from OMT (0.873, 0.809, and 0.823). GAAP achieved an AUC of 0.922 in the test dataset.Conclusion: GALAD was excellent for discrimination of HCC from CLD in the HCV subgroup of a cohort of Chinese patients. The GAAP and GALAD-C models achieved better performance compared with GALAD. These three models exhibited better performance in patients with an HCV etiology than those with HBV.Keywords: hepatocellular carcinoma, alpha-fetoprotein, PIVKA-II, GALAD

During root nodule symbiosis, intracellular accommodation of rhizobia by legumes is a prerequisite for nitrogen fixation. For many legumes, rhizobial colonization initiates in root hairs through transcellular infection threads. In Medicago truncatula, VAPYRIN (VPY) and a putative E3 ligase LUMPY INFECTIONS (LIN) are required for infection thread development but their cellular and molecular roles are obscure. Here we show that LIN and its homolog LIN-LIKE interact with VPY and VPY-LIKE in a subcellular complex localized to puncta both at the tip of the growing infection thread and at the nuclear periphery in root hairs and that the punctate accumulation of VPY is positively regulated by LIN. We also show that an otherwise nuclear and cytoplasmic exocyst subunit, EXO70H4, systematically co-localizes with VPY and LIN during rhizobial infection. Genetic analysis shows that defective rhizobial infection in exo70h4 is similar to that in vpy and lin. Our results indicate that VPY, LIN and EXO70H4 are part of the symbiosis-specific machinery required for polar growth of infection threads.

During root nodule symbiosis, intracellular accommodation of rhizobia by legumes is a prerequisite for nitrogen fixation. For many legumes, rhizobial colonization initiates in root hairs through transcellular infection threads. In Medicago truncatula, VAPYRIN (VPY) and a putative E3 ligase LUMPY INFECTIONS (LIN) are required for infection thread development but their cellular and molecular roles are obscure. Here we show that LIN and its homolog LIN-LIKE interact with VPY and VPY-LIKE in a subcellular complex localized to puncta both at the tip of the growing infection thread and at the nuclear periphery in root hairs and that the punctate accumulation of VPY is positively regulated by LIN. We also show that an otherwise nuclear and cytoplasmic exocyst subunit, EXO70H4, systematically co-localizes with VPY and LIN during rhizobial infection. Genetic analysis shows that defective rhizobial infection in exo70h4 is similar to that in vpy and lin. Our results indicate that VPY, LIN and EXO70H4 are part of the symbiosis-specific machinery required for polar growth of infection threads.