The unequal functional redundancy of Arabidopsis INCURVATA11 and CUPULIFORMIS2 is not dependent on genetic background

The paralogous genes INCURVATA11 (ICU11) and CUPULIFORMIS2 (CP2) encode components of the epigenetic machinery in Arabidopsis and belong to the 2-oxoglutarate and Fe (II)-dependent dioxygenase superfamily. We previously inferred unequal functional redundancy between ICU11 and CP2 from a study of the synergistic phenotypes of the double mutant and sesquimutant combinations of icu11 and cp2 mutations, although they represented mixed genetic backgrounds. To avoid potential confounding effects arising from different genetic backgrounds, we generated the icu11-5 and icu11-6 mutants via CRISPR/Cas genome editing in the Col-0 background and crossed them to cp2 mutants in Col-0. The resulting mutants exhibited a postembryonic-lethal phenotype reminiscent of strong embryonic flower (emf) mutants. Double mutants involving icu11-5 and mutations affecting epigenetic machinery components displayed synergistic phenotypes, whereas cp2-3 did not besides icu11-5. Our results confirmed the unequal functional redundancy between ICU11 and CP2 and demonstrated that it is not allele or genetic background specific. An increase in sucrose content in the culture medium partially rescued the post-germinative lethality of icu11 cp2 double mutants and sesquimutants, facilitating the study of their morphological phenotypes throughout their life cycle, which include floral organ homeotic transformations. We thus established that the ICU11-CP2 module is required for proper flower organ identity

The m6A RNA demethylase ALKBH9B plays a critical role for vascular movement of Alfalfa mosaic virus in Arabidopsis

[EN] The N-6-methyladenosine (m(6)A) pathway has been widely described as a viral regulatory mechanism in animals. We previously reported that the capsid protein (CP) of alfalfa mosaic virus (AMV) interacts with the Arabidopsis m(6)A demethylase ALKBH9B regulating m(6)A abundance on viral RNAs (vRNAs) and systemic invasion of floral stems. Here, we analyze the involvement of other ALKBH9 proteins in AMV infection and we carry out a detailed evaluation of the infection restraint observed in alkbh9b mutant plants. Thus, via viral titer quantification experiments and in situ hybridization assays, we define the viral cycle steps that are altered by the absence of the m(6)A demethylase ALKBH9B in Arabidopsis. We found that ALKBH9A and ALKBH9C do not regulate the AMV cycle, so ALKBH9B activity seems to be highly specific. We also define that not only systemic movement is affected by the absence of the demethylase, but also early stages of viral infection. Moreover, our findings suggest that viral upload into the phloem could be blocked in alkbh9b plants. Overall, our results point to ALKBH9B as a possible new component of phloem transport, at least for AMV, and as a potential target to obtain virus resistance crops.This research was funded by the Spanish Agencia Estatal de Investigacion (AEI), grant numbers PID2020-115571RB-I00 to VP, and PGC2018-093445-B-I00 to JLM. MM-P was recipient of Predoctoral Contract FPI-2015-072406 from the Subprograma Formacion de Personal InvestigadorMinisterio de Economia y Competitividad (FPI-MINECO). LA-M was recipient of a Predoctoral contract from the Ministerio de Ciencia, Tecnologia y Telecomunicaciones from Costa Rica (MICITT-PINN-CON-624-2019). RN was recipient of the GRISOLIAP/2016/131 Predoctoral Contract from the Generalitat Valenciana.Martínez-Pérez, M.; Gómez Mena, MC.; Alvarado-Marchena, L.; Nadi, R.; Micol, JL.; Pallás Benet, V.; Aparicio Herrero, F. (2021). The m6A RNA demethylase ALKBH9B plays a critical role for vascular movement of Alfalfa mosaic virus in Arabidopsis. Frontiers in Microbiology. 12:1-13. https://doi.org/10.3389/fmicb.2021.745576S1131