FRUCTOKINASE-LIKE PROTEINS (FLNs) are phosphofructokinase-B (PfkB)-type
carbohydrate kinases that act as part of the PEP complex, which are known to
transcribe chloroplast genes. However, the mechanisms underlying FLNs
activity in rice remain elusive. Previously, the team of Lei He from China
National Rice Research Institute studied a heat-stress sensitive albino
mutant in rice, hsa1. Analysis of this mutant revealed that HSA1 gene
encodes an OsFLN2 protein.

Using CRISPR-Cas9 technology, the team aimed to prove that knockdown or
knockout of the OsFLN1, a homolog of HSA1/OsFLN2, will inhibit chloroplast
biogenesis. The fln1 knockout mutants exhibited severe albino phenotype and
seedling lethality. Analysis found that OsFLN1 localizes in the chloroplast
and that the OsFLN1 and HSA1/OsFLN2 proteins interact with THIOREDOXINZ
(OsTRXz) to regulate chloroplast development.

To prove this, OsTRXz knockout plants were developed and it resulted in
similar albino and seedling lethal phenotype as the fln1 mutants.

These results show that OsFLN1 and HSA1/OsFLN2 contribute to chloroplast
biogenesis and plant growth.

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