Leaf chlorosis and bleach in plants under formaldehyde (HCHO) stress has been observed in previous studies. To better understand the mechanism of HCHO inhibition on photosynthesis, effects of HCHO stress on physiological characteristics and gene expression associated with photosynthesis in Arabidopsis thaliana were investigated in this study. The results indicated that HCHO stress reduced total chlorophyll (Chl) and Chl b content but increased Chl a content and a/b ratio in Arabidopsis. Suppression subtractive hybridization analysis identified 22 potential HCHO-repressive genes associated with photosynthesis. Furthermore, RT-PCR data showed that transcriptional levels of Lhcb2.1, Lhcb3, Lhca4, RBCS1A, RCA, Psao, Psbo, and Psbp were reduced to their lowest levels at 4 h after Arabidopsis was treated with 2–4 mM HCHO. The restoration in expression levels of Lhcb3, Lhca4, RBCS1A, and Psbp as well as up-regulation in Lhcb2.1 and RCA transcription was observed from 12 to 24 h after HCHO treatment. 13C-NMR analysis revealed that change patterns of endogenous glucose content were similar to expression patterns of these genes under HCHO stress from 0.5 to 24 h. The glucose content decreased to the lowest level at 4 h, accompanied by a potent inhibition on the capacity of CO2 assimilation caused by exogenous HCHO. From 4 to 24 h of HCHO stress, exogenous HCHO was efficiently metabolized and converted to glucose, which allowed the glucose content to be restored to its original level; thus, repressive effects of HCHO stress on expressions of photosynthesis-related genes were eliminated. These results suggested a correlation between HCHO metabolic level and expression levels of photosynthesis-related genes in vivo during this period. However, a second reduction in expressions of these genes after 36 h might be attributed to other effects triggered by HCHO stress.
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