22-Nucleotide RNAs trigger secondary siRNA biogenesis in plants.

The effect of RNA silencing in plants can be amplified if the production of secondary small interfering RNAs (siRNAs) is triggered by the interaction of microRNAs (miRNAs) or siRNAs with a long target RNA. miRNA and siRNA interactions are not all equivalent, however; most of them do not trigger secondary siRNA production. Here we use bioinformatics to show that the secondary siRNA triggers are miRNAs and transacting siRNAs of 22 nt, rather than the more typical 21-nt length.

LZF1, a HY5-regulated transcriptional factor, functions in Arabidopsis de-etiolation.

We surveyed differential gene expression patterns during early photomorphogenesis in both wild-type and mutant Arabidopsis defective in HY5, an influential positive regulator of the responses of gene expression to a light stimulus, to identify light-responsive genes whose expression was HY5 dependent. These gene-expression data identified light-regulated zinc finger protein 1 (LZF1), a gene encoding a previously uncharacterized C2C2-CO B-box transcriptional regulator. HY5 has positive trans-activating activity toward LZF1 and binding affinity to LZF1 promoter in vivo.