Identification of two recessive etiolation genes (py1, py2) in pakchoi (Brassica rapa L. ssp. chinensis)

Abstract

Background: Leaf color is a major agronomic trait, which has a strong influence on crop yields. Isolating leaf color mutants can represent valuable materials for research in chlorophyll (Chl) biosynthesis and metabolism regulation. Results: In this study, we identified a stably inherited yellow leaf mutant derived from 'Huaguan' pakchoi variety via isolated microspore culture and designated as pylm. This mutant displayed yellow leaves after germination. Its etiolated phenotype was nonlethal and stable during the whole growth period. Its growth was weak and its hypocotyls were markedly elongated. Genetic analysis revealed that two recessive nuclear genes, named py1 and py2, are responsible for the etiolation phenotype. Bulked segregant RNA sequencing (BSR-Seq) showed that py1 and py2 were mapped on chromosomes A09 and A07, respectively. The genes were single Mendelian factors in F 3:4 populations based on a 3:1 phenotypic segregation ratio. The py1 was localized to a 258.3-kb interval on a 34-gene genome. The differentially expressed gene BraA09004189 was detected in the py1 mapping region and regulated heme catabolism. One single-nucleotide polymorphism (SNP) of BraA09004189 occurred in pylm. A candidate genespecific SNP marker in 1520 F 3:4 yellow-colored individuals co-segregated with py1. For py2, 1860 recessive homozygous F 3:4 individuals were investigated and localized py2 to a 4.4-kb interval. Of the five genes in this region, BraA07001774 was predicted as a candidate for py2. It encoded an embryo defective 1187 and a phosphotransferase related to chlorophyll deficiency and hypocotyl elongation. One SNP of BraA07001774 occurred in pylm. It caused a single amino acid mutation from Asp to Asn. According to quantitative real-time polymerase chain reaction (qRT-PCR), BraA07001774 was downregulated in pylm. Conclusions: Our study identified a Chl deficiency mutant pylm in pakchoi. Two recessive nuclear genes named py1 and py2 had a significant effect on etiolation. Candidate genes regulating etiolation were identified as BraA09004189 and BraA07001774, respectively. These findings will elucidate chlorophyll metabolism and the molecular mechanisms of the gene interactions controlling pakchoi etiolation.

Comparative transcriptome and microbial community sequencing provide insight into yellow-leaf phenotype of Camellia japonica

“…For example, the undeveloped thylakoid membranes and yellow leaf phenotype of peas were caused by virus-induced silencing of CHLI and CHLD genes [13]. Over the past few decades, leaf yellowing mutants, such as Cucumis sativus [14,15], maize [16], rice [17], wheat [18,19], Camellia sinensis [20], Brassica rapa [21], and Arabidopsis thaliana [22,23], have been identified in many plants. These mutants have been widely used in basic research.…”

Cytological, Physiological, and Transcriptomic Analyses of the Leaf Color Mutant Yellow Leaf 20 (yl20) in Eggplant (Solanum melongena L.)

“…The leaf samples were obtained at 30 and 90 days after sowing. For chlorophyll extraction, 0.3 g fresh leaf samples were extracted using previously described methods [ 25 ]. The supernatants were collected to assess Chl a , Chl b , total chlorophyll, and carotenoid contents using an ultraviolet-visible spectrophotometer (UV-7500, Shanghai MAPADA Instruments Co., Ltd., Shanghai, China).…”

“…Proteomic analysis of yellow and green G. biloba leaves can help identify the differentially expressed proteins related to energy metabolism, photosynthesis, and carbon fixation [ 19 ]. Over the past few decades, yellow leaf mutants of various crops, such as cucumber [ 7 , 20 ], maize [ 21 ], rice [ 22 ], wheat [ 23 , 24 ], and pakchoi [ 25 ], have been identified. Eggplant ( Solanum melongena L.) is a popular vegetable crop, especially in Asia, Africa, the Mediterranean coast, and south-central Europe.…”

Advance in mechanism of plant leaf colour mutation

“…Many leaf colour mutants caused by abnormal heme metabolism have been identified, including A. thaliana (Xie et al, 2012), O. sativa (Xu et al, 2012;Li et al, 2014), Pisum sativum (Linley et al, 2006), Zea mays (Shi et al, 2013), and Brassica pekinensis (Zhang et al, 2020). Studies on the yellow leaf colour mutant pylm showed that the single-base mutation of recessive nuclear genes (PY1 and PY2), results in the dysfunction of heme oxygenase-1 (HO-1) (Zhang et al, 2020). The accumulation of excessive heme in leaves activates the feedback inhibition of Chl synthesis (Weller et al, 1996), leading to the expression of the yellow leaf phenotype.…”