The Rice Qa-SNAREs in SYP13 Subfamily Are Involved in Regulating Arbuscular Mycorrhizal Symbiosis and Seed Fertility.

Qa-SNARE gene (isoform α) was previously reported to affect arbuscular mycorrhizal (AM) symbiosis in the legume species . In non-legumes especially monocots, it remains unknown whether certain genes are also involved in AM symbiosis. In this work, we studied a rice orthologous gene , which showed induced expression in mycorrhizal roots and two paralogous genes and , which were not induced by the AM fungus . After employing CRISPR/Cas9 technique to generate their mutants, the homozygous mutant T plants exhibited a dwarf phenotype and produced no fertile seeds, indicating a required role of this gene in seed fertility. Unlike the case in legume, the mutants exhibited normal mycorrhizal phenotype, so did the mutants. In the double mutants, however, the colonization rate and arbuscule abundance level decreased markedly, indicating an impaired fungal proliferation ability in rice roots. Such a defect was further confirmed by the reduced expression levels of AM marker genes. Our results in rice therefore demonstrated that while SYP13II members showed evolutionary and induction patterns specific to symbiosis, AM symbiosis is in fact controlled by the combined action of both SYP13I and SYP13II clades, revealing a functional redundancy among SYNTAXIN genes in mutualism.