The poly(A) polymerase PAPS1 mediates pollen maturation by regulating sperm cell differentiation in plants

In flowering plants, a haploid microspore undergoes an asymmetric division to produce the male germline that encounters a mitotic division to produce two germ cells. The resulting germ cells undergo a series of specialization events to produce the two sperm cells required for double fertilization. These events include to upregulate male germline‐specific while downregulating male germline‐nonspecific regulon, but how these specializations events are regulated, are still unresolved. To know how plant sperm cell is specialized, we mutagenized Arabidopsis double homozygous transgenic line (MGH3p‐MGH3::eGFP and ACTIN11p‐H2B::mRFP) by an ethyl methane sulfonate (EMS) treatment and isolated a mutant with sperms identity loss, resulting in a completely male defective plant. Second‐generation sequencing identified a point mutation G/A causing premature stop codon TGG/TGA in the poly(A) polymerase PAPS1 that is linked with phenotype. Further, we found that paps1 mutant fails to upregulate male germline‐specific regulon and to downregulate male germline‐nonspecific factors required for sperm cell differentiation and attaining pollen maturation. Previously, polyadenylation of pre‐mRNAs by PAPS1 has been found crucial for both RNA‐based silencing processes and the processing of pre‐mRNAs into mature mRNAs ready for translation. This study concludes that PAPS1 mediates sperm cell differentiation through upregulating specific while silencing the nonspecific factors of male germlines.