Cold acclimation can specifically inhibit chlorophyll biosynthesis in young leaves of Pakchoi

Abstract

Background Leaf color is an important trait in breeding of leafy vegetables. Y-05, a pakchoi (Brassica rapa ssp. chinensis) cultivar, displays yellow inner (YIN) and green outer leaves (GOU) after cold acclimation. However, the mechanism of this special phenotype remains elusive. Results We assumed that the yellow leaf phenotype of Y-05 maybe caused by low chlorophyll content. Pigments measurements and transmission electron microscopy (TEM) analysis showed that the yellow phenotype is closely related with decreased chlorophyll content and undeveloped thylakoids in chloroplast. Transcriptomes and metabolomes sequencing were next performed on YIN and GOU. The transcriptomes data showed that 4887 differentially expressed genes (DEGs) between the YIN and GOU leaves were mostly enriched in the chloroplast- and chlorophyll-related categories, indicating that the chlorophyll biosynthesis is mainly affected during cold acclimation. Together with metabolomes data, the inhibition of chlorophyll biosynthesis is contributed by blocked 5-aminolevulinic acid (ALA) synthesis in yellow inner leaves, which is further verified by complementary and inhibitory experiments of ALA. Furthermore, we found that the blocked ALA is closely associated with increased BrFLU expression, which is indirectly altered by cold acclimation. In BrFLU-silenced pakchoi Y-05, cold-acclimated leaves still showed green phenotype and higher chlorophyll content compared with control, meaning silencing of BrFLU can rescue the leaf yellowing induced by cold acclimation. Conclusions Our findings suggested that cold acclimation can indirectly promote the expression of BrFLU in inner leaves of Y-05 to block ALA synthesis, resulting in decreased chlorophyll content and leaf yellowing. This study revealed the underlying mechanisms of leaves color change in cold-acclimated Y-05.

Understanding and Comprehensive Evaluation of Cold Resistance in the Seedlings of Multiple Maize Genotypes

“…Chlorophyll is an essential cofactor for photosynthesis, and maintaining a normal chlorophyll state and level is essential for photosynthetic efficiency and carbon fixation, which directly influence plant growth and development under various abiotic stresses [ 18 ]. Comparing seedlings of 39 maize genotypes exposed to 10 °C low-temperature stress with 22 °C control, 10 °C significantly reduced the contents of Chl a, Chl b, Chl a+b in their leaves by 18.6%, 21.7%, and 20.3%, respectively; however, chlorophyll a:b ratio (Chl a/b) slightly increased by 3.3% ( Figure 1 and Figure 2 ).…”

CfCHLM, from Cryptomeria fortunei, Promotes Chlorophyll Synthesis and Improves Tolerance to Abiotic Stresses in Transgenic Arabidopsis thaliana

“…In this study, the expression of CfCHLM in C. fortunei was shown to be downregulated under abiotic stress, and the downregulation of the CHLM gene may have inhibited the synthesis of chl. Many studies have shown that the synthesis of chl is inhibited under various abiotic stresses [28][29][30][31], which demonstrates the downregulation of the CfCHLM gene in response to stress.…”

Recent applications of metabolomics in plant breeding

“…In an important study on the mechanism of stress response, Wang et al (2021) identified the fluorescence in blue light (BrFLU) gene in Pak Choi; the gene was shown to be related to cold acclimation in a study that combined transcriptomics methods.…”