24-nt phasiRNAs move from tapetal to meiotic cells in maize anthers

Abstract

In maize, 24-nt phased, secondary small interfering RNAs (phasiRNAs) are abundant in meiotic stage anthers, but their distribution and functions are not precisely known. Using laser capture microdissection we analyzed tapetal cells, meiocytes, and other somatic cells at several stages of anther development to establish the timing of 24-PHAS precursor transcripts and the 24-nt phasiRNA products. By integrating RNA and small RNA (sRNA) profiling plus single-molecule and sRNA FISH (smFISH or sRNA-FISH) spatial detection, we demonstrate that the tapetum is the primary site of 24-PHAS precursor and Dcl5 transcripts and the resulting 24-nt phasiRNAs. Interestingly, 24-nt phasiRNAs accumulate in all cell types, with the highest levels in meiocytes, followed by tapetum. Our data support the conclusion that 24-nt phasiRNAs are mobile from tapetum to meiocytes and to other somatic cells. We discuss possible roles for 24-nt phasiRNAs in anther cell types.

3D-multiple immunoimaging using whole male organs in rice

“…A large number of 21- and 24-nucleotide small RNAs are produced specifically in the anther and are loaded into the reproductive AGOs 19,20 . It has also been reported that 24-nt small RNAs of the anther move from the tapetum to the meiocytes 21 , indicating the possibility of non-cell-autonomous control via small RNAs as mobile signals in anthers. Hence, the method will also have potential applicability in observing the multiple localization of proteins and RNAs.…”

Plant non-coding RNAs function in pollen development and male sterility

“…miR2275 is specifically expressed in the tapetum during the early meiosis stage, and its expression is quickly reduced in other stages of male gametogenesis in both rice and maize ( Tamim et al., 2018 ). In maize, the tapetum is the primary site of the 24-PHAS precursor and Dcl5 transcripts, as well as the resulting 24-nt phasiRNAs, and then the phasiRNAs are mobile from the tapetum to meiocytes and to other somatic cells ( Zhou et al., 2022 ). Generally, maize male-sterile mutants with subepidermal defects lack 24-nt phasiRNAs ( Zhai et al., 2015 ).…”