Genetic mapping and candidate gene identification of BoGL5, a gene essential for cuticular wax biosynthesis in broccoli

Fengqing Han,Limei Yang,Qi Xie,Yangyong Zhang,Jingjing Huang,Mu Zhuang,Honghao Lv,Jialei Ji,Yong Wang,Zhiyuan Fang,Zhansheng Li,Yumei Liu

doi:10.1186/s12864-021-08143-7

Fengqing Han, Limei Yang + Show 10 more

Open Access

https://doi.org/10.1186/s12864-021-08143-7

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Abstract

BackgroundThe aerial organs of most terrestrial plants are covered by cuticular waxes, which impart plants a glaucous appearance and play important roles in protecting against various biotic and abiotic stresses. Despite many glossy green (wax-defective) mutants being well characterized in model plants, little is known about the genetic basis of glossy green mutant in broccoli.ResultsB156 is a spontaneous broccoli mutant showing a glossy green phenotype. Detection by scanning electron microscopy (SEM) and chromatography-mass spectrometry (GC-MS) revealed that B156 is a cuticular wax-defective mutant, lacking waxes mostly longer than C28. Inheritance analysis revealed that this trait was controlled by a single recessive gene, BoGL5. Whole-genome InDel markers were developed, and a segregating F2 population was constructed to map BoGL5. Ultimately, BoGL5 was mapped to a 94.1 kb interval on C01. The BoCER2 gene, which is homologous to the Arabidopsis CER2 gene, was identified as a candidate of BoGL5 from the target interval. Sequence analyses revealed that Bocer2 in B156 harbored a G-to-T SNP mutation at the 485th nucleotide of the CDS, resulting in a W-to-L transition at the 162nd amino acid, a conserved site adjacent to an HXXXD motif of the deduced protein sequence. Expression analysis revealed that BoCER2 was significantly down-regulated in the leaves, stems, and siliques of B156 mutant than that of B3. Last, ectopic expression of BoCER2 in A. thaliana could, whereas Bocer2 could not, rescue the phenotype of cer2 mutant.ConclusionsOverall, this study mapped the locus determining glossy phenotype of B156 and proved BoCER2 is functional gene involved in cuticular wax biosynthesis which would promotes the utilization of BoCER2 to enhance plant resistance to biotic and abiotic stresses, and breeding of B. oleracea cultivars with glossy traits.

Highlights

The aerial organs of most terrestrial plants are covered by cuticular waxes, which impart plants a glaucous appearance and play important roles in protecting against various biotic and abiotic stresses
Observation by scanning electron microscopy (SEM) revealed that B3 leaves were covered with rod-shaped wax crystals, whereas B156 leaves were nearly devoid of wax crystals (Fig. 1C and F)
All waxes longer than C28, except for C29 aldehydes, were dramatically decreased; in contrast C26, C27 and C28 waxes were slightly increased (Fig. 1G), indicating elongation of C28 very long chain fatty acids (VLCFAs) was blocked in B156 mutant

Summary

Introduction

The aerial organs of most terrestrial plants are covered by cuticular waxes, which impart plants a glaucous appearance and play important roles in protecting against various biotic and abiotic stresses. In Arabidopsis thaliana, many wax-biosynthesis genes have been identified, including the FAE complex genes KCS1, KCS2, KCS6, KCS9, KCS20 and KCR1 [7, 8]; the VLCFA modification genes CER4, MAH1, CER1, CER3, CER2 (−like) and CER26 [9–11]; the transporter genes DESPERADO/AtWBC11, ABCG transporters, and the CER5 gene [12, 13]; and the regulatory genes WIN1/ SHN1, SHN2, SHN3, MYB30, MYB41, CFL1, CER7, and CER9 [14, 15]. Mutants of these wax-related genes show a decrease or lack of cuticular waxes, resulting in glossy phenotypes

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