Single Nucleotide Mutagenesis of the TaCHLI Gene Suppressed Chlorophyll and Fatty Acid Biosynthesis in Common Wheat Seedlings

Abstract

Wheat (Triticum aestivum L.) is one of the most important crops in the world. Chlorophyll plays a vital role in plant development and crop improvement and further determines the crop productivity to a certain extent. The biosynthesis of chlorophyll remains a complex metabolic process, and fundamental biochemical discoveries have resulted from studies of plant mutants with altered leaf color. In this study, we identified a chlorophyll-deficiency mutant, referred to as chli, from the wheat cultivar Shaannong33 that exhibited an obvious pale-green leaf phenotype at the seedling stage, with significantly decreased accumulation of chlorophyll and its precursors, protoporphyrin IX and Mgprotoporphyrin IX. Interestingly, a higher protoporphyrin IX to Mg-protoporphyrin IX ratio was observed in chli. Lipid biosynthesis in chli leaves and seeds was also affected, with the mutant displaying significantly reduced total lipid content relative to Shaanong33. Genetic analysis indicated that the pale-green leaf phenotype was controlled by a single pair of recessive nuclear genes. Furthermore, sequence alignment revealed a single-nucleotide mutation (G664A) in the gene TraesCS7A01G480700.1, which encodes subunit I of the Mg-chelatase in plants. This single-nucleotide mutation resulted in an amino acid substitution (D221N) in the highly conserved domain of subunit I. As a result, mutant protein Tachli-7A lost the ability to interact with the normal protein TaCHLI-7A, as assessed by yeast two-hybrid assay. Meanwhile, Tachli-7A could not recover the chlorophyll deficiency phenotype of the Arabidopsis thaliana SALK_050029 mutant. Furthermore, we found that in Shaannong33, the protoporphyrin IX to Mgprotoporphyrin IX ratio was growth state-dependent and insensitive to environmental change. Overall, the mutation in Tachli-7A impaired the function of Mg-chelatase and blocked the conversion of protoporphyrin IX to Mg-protoporphyrin IX. Based on our results, the chli mutant represents a potentially useful resource for better understanding chlorophyll and lipid biosynthetic pathways in common wheat.

Mapping of a Pale Green Mutant Gene and Its Functional Verification by Allelic Mutations in Chinese Cabbage (Brassica rapa L. ssp. pekinensis)

“…For example, Li et al ( 2020 ) found that a single nucleotide substitution in sedoheptulose 1,7-bisphosphatase ( SBPase ) severely affects plant growth and grain yield in rice. A single nucleotide mutation (G664A) in the TraesCS7A01G480700.1 ( chlI of Mg-chelatase) resulted in the mutant protein losing the ability to interact with the normal protein TaCHLI-7A (Wang et al, 2020 ). In A. thaliana , a single nucleotide substitution in DVR leading to one amino acid substitution in the protein did a partial loss of DVR function.…”

Transcriptome Analysis Reveals Potential Mechanism in Storage Protein Trafficking within Developing Grains of Common Wheat

“…Shaannong 33 is a newly released high-quality, strong gluten wheat variety that has been approved in Shaanxi Province and introduced in Henan Province, China [ 88 , 89 ]. A summary and details of Shaannong 33 are shown in Table 4 , and the sister line of Shaannong 33, used as the control (CK), reported with low-quality traits, given in Table 1 , represents three-year field trails.…”

DNA Methylation and RNA-Sequencing Analysis to Identify Genes Related to Spontaneous Leaf Spots in a Wheat Variety ‘Zhongkenuomai No.1’

“…Leaf color variation is an important mutation for improving photosynthesis and increasing yield potential. In fact, several stably inheritable leaf color variations have been discovered in wheat (Dlm, lm3, Ygm and chli), providing abundant genetic resources for breeding wheat with high photosynthetic efficiency and ideal yield potential [4][5][6][7]. Most leaf color mutants can be primarily divided into two types: homogeneous (just one leaf color: albina, xantha mutations) and heterogeneous (two or more leaf colors: alboviridis, viridis, or tigrina mutations).…”

“…Furthermore, displaying distinct leaf colors at different growth phases would result in a more diversified and perceptible leaf landscape. Wang et al reported a pale-green leaf mutant (chli) presenting greenish leaves from the one-leaf stage and re-green at the heading stage [7]. The results revealed no change in kernel quantity or seed setting rate with the wide type, but a notable reduction in tiller number.…”