Transgenerational conditioned male fertility of HD-ZIP IV transcription factor mutant ocl4: impact on 21-nt phasiRNA accumulation in pre-meiotic maize anthers

Plant Reprod. 2021 Jun;34(2):117-129. doi: 10.1007/s00497-021-00406-3. Epub 2021 Mar 10.

Abstract

Maize Outer cell layer 4 (ocl4) encodes an HD-ZIP IV transcription factor required for robust male fertility and 21-nt phasiRNA biogenesis. ocl4 fertility is favored in warm conditions, and phasiRNAs are partially restored. Environment-sensitive male-sterile plants have been described before and can result from different molecular mechanisms and biological processes, but putative environment-conditioned, transgenerational rescue of their male fertility is a rather new mystery. Here, we report a derivative line of the male-sterile outer cell layer 4 (ocl4) mutant of maize, in which fertility was restored and perpetuated over several generations. Conditioned fertile ocl4 anthers exhibit the anatomical abnormality of a partially duplicated endothecial layer, just like their sterile counterparts. We profiled the dynamics of phased, small interfering RNAs (phasiRNAs) during pre-meiotic development in fully sterile and various grades of semi-fertile ocl4 anthers. The conditioned fertile anthers accumulated significantly higher 21-nt phasiRNAs compared to ocl4 sterile samples, suggesting a partial restoration of phasiRNAs in conditioned fertility. We found that the biogenesis of 21-nt phasiRNAs is largely dependent on Ocl4 at three key steps: (1) production of PHAS precursor transcripts, (2) expression of miR2118 that modulates precursor processing, and (3) accumulation of 21-nt phasiRNAs.

Keywords: Conditioned fertility; Maize; Male sterility; Ocl4; PhasiRNA.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Fertility / genetics
  • Gene Expression Regulation, Plant
  • RNA, Plant
  • Transcription Factors*
  • Zea mays* / genetics

Substances

  • RNA, Plant
  • Transcription Factors