Spatiotemporal regulation of target mRNA cleavage by 21-nt phasiRNAs in maize anthers [RNA-seq]

In grasses, 21- and 24-nt phasiRNAs are abundantly expressed in anthers and play crucial roles in anther development and male reproduction. 21-nt phasiRNAs can act in cis to direct the cleavage of their own precursor transcripts and is thought to lack trans cleavage targets in maize. Here we show that 21-nt phasiRNAs direct the cleavage of hundreds of target mRNAs in maize, with the cleavage activity being enriched in male germ cells. Interestingly, whereas 21-nt phasiRNAs in anthers (somatic anther wall cells) do not have obvious preference for a particular nucleotide at the 5' end and target genes implicated in stress response and cellular homeostasis, 21-nt phasiRNAs in male germ cells preferentially initiate with 5' C and associate with ZmAGO5c/MAGO2/MS28 to target genes related to meiotic processes. Our results indicate that mRNA cleavage is a conserved mechanism used by 21-nt phasiRNAs for gene regulation. However, the sequences of 21-nt phasiRNAs and their targets show low conservation in maize and rice, suggesting that 21PHAS loci and 21-nt phasiRNA targets have undergone fast divergence in monocots. Overall design: To explore potential targets of 21-nt phasiRNA and their regulatory roles in their targets in maize,we collected maize anthers,male germ cells across various these developmental stages. and embryos from seeds .We then using these samples performed low-input sRNA-seq, RNA-seq and high sensitive degradome-seq