Dicer-like 5 deficiency confers temperature-sensitive male sterility in maize

Small RNAs play important roles during plant development by regulating transcript levels of target mRNAs, maintaining genome integrity, and reinforcing DNA methylation. Dicer-like 5 ( Dcl5 ) is proposed to be responsible for precise slicing to generate diverse 24-nt phased, secondary small interfering RNAs (phasiRNAs), which are exceptionally abundant in meiotic anthers of maize, rice, and other grasses 1. The importance and functions of these phasiRNAs remain unclear. Here, we used the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) Cas9 system to mutate Dcl5 . We report that dcl5 mutants have few or no 24-nt phasiRNAs, develop short anthers and defective tapetal cells, and exhibit temperature-sensitive male fertility. We propose that DCL5 and 24-nt phasiRNAs are critical for fertility under growth regimes for optimal yield.