Fine mapping of a candidate gene for cool-temperature-induced albinism in ornamental kale

Abstract

Background The symptoms of cool-temperature-induced chlorosis (CTIC) are widely existed in higher plants. Although many studies have shown that the genetic mechanism of CTIC is generally controlled by recessive genes in model plants, the dominant inheritance of albinism has not been reported thus far. Here, two CTIC mutants, Red Kamome and White Kamome, were utilized to analyse the inheritance of the albino trait in ornamental kale. The objective of this investigation is to fine-map the target locus and identify the most likely candidate genes for albinism. Results Genetic analysis revealed that the albinism in the inner leaves of ornamental kale followed semi-dominant inheritance and was controlled by a single locus in two segregating populations. BSR-seq in combination with linkage analysis was employed to fine-map the causal gene, named AK (Albino Kale), to an approximate 60 kb interval on chromosome C03. Transcriptome data from two extreme pools indicated that the differentially expressed gene of Bol015404, which encodes a cytochrome P450 protein, was the candidate gene. The Bol015404 gene was demonstrated to be upregulated in the albino leaves of ornamental kale by qPCR. Additionally, the critical temperature for the albinism was determined between 10 °C and 16 °C by gradient test. Conclusions Using two independent segregating populations, the albino mutants were shown to be controlled by one semi-dominant gene, AK, in ornamental kale. The Bol015404 gene was co-segregated with albinism phenotypes, suggesting this unknown function P450 gene as the most likely candidate gene. The albino trait appeared caused by the low temperatures rather than photoperiod. Our results lay a solid foundation on the genetic control of albinism in ornamental kale.

Transcriptome Analysis of Green and White Leaf Ornamental Kale Reveals Coloration-Related Genes and Pathways

“…Abnormal chloroplast development is a major reason for the formation of chlorophyll-deficient mutants ( Zhang et al, 2020 ). Previous studies have shown that the white leaf of ornamental kale formation was mainly due to chloroplast deficiency ( Zhou et al, 2013 ; Yan et al, 2020 ). Chloroplast biogenesis involved several functional processes including thylakoid formation, pigment synthesis, plastid divisions, retrograde signaling, etc.…”

“…The molecular mechanisms of white leaf formation are complex and related to multiple biochemical processes and genes in different ornamental kale cultivars. Yan et al (2020) identified the cytochrome P450 gene ( Bol015404 ) as the most likely candidate gene for white leaf formation of ornamental kale by using BSR-seq. In this study, this gene was a significantly high expression in white leaf tissue than that in the green leaf tissue [log 2 (W/G) = 12.071, log 2 (W1/G2) = 1.322].…”

“…These results are consistent but seem to be more closely with the comparison group of G02 vs. 1631. It is worth mentioning that in the study of Yan et al (2020) , a single peak occurred in chromosome C01, which may correspond to the PSBQ gene ( Bo1g158910 ). This result further indicated that PSBQ may be involved in the formation of the white leaf.…”

“…The color of the cultivar will turn completely white when under low-temperature conditions, and can turn green again under normal temperature conditions (>16°C). Recent studies have shown that the white phenotype might be caused by inhibiting chlorophyll biosynthesis and chloroplast development ( Zhou et al, 2013 ; Yan et al, 2020 ). However, the study on the color development detailed molecule mechanism of white and green leaf ornamental kale has not been reported.…”

Identification of Novel Locus RsCr6 Related to Clubroot Resistance in Radish (Raphanus sativus L.)

“…Additionally, the two parental lines were subjected to resequencing with 30 × depth. As previously described (Yan et al, 2020 ), BSA-seq analysis was performed using a user-friendly script. The clean reads from two pools were aligned against the long-read reference genome “QZ-16” (ENA number: PRJEB37015) by Bowtie (Langmead and Salzberg, 2012 ).…”