In land plants, chloroplast transcripts undergo post-transcriptional
modifications, including splicing, editing, trimming, before translation.
This essential step is regulated by a set of nuclear-encoded proteins.
Zhong-wei Wang from the China National Rice Research Institute characterized
a rice (Oryza sativa) seedling-lethal albino mutant, sla4.
The sla4 mutant exhibited an albino phenotype from germination through the
third-leaf stage, and then gradually died. The sla4 mutants also lacked
photosynthetic pigments and had severe defects in photosynthesis and early
chloroplast development. Analysis showed that a 13-base pair deletion in the
coding region of OsSLA4 on chromosome 7 resulted in the albino phenotype.
The albino mutants were also generated by knocking-out OsSLA4 using the
CRISPR-Cas9 system. OsSLA4 was found to encode a chloroplast-localized
pentatricopeptide repeat (PPR) protein.
Loss-of-function of OsSLA4 resulted in severe defects in the intron splicing
of several genes as well as a significant reduction in the transcript levels
of chloroplast ribosomal RNAs and some chloroplast development- and
These results indicate that OsSLA4 is important for early chloroplast
development and seedling growth in rice.