title: Copy Number Variation of Cytokinin Oxidase Gene Tackx4 Associated with Grain Weight and Chlorophyll Content of Flag Leaf in Common Wheat.
abstract: As the main pigment in photosynthesis, chlorophyll significantly affects grain filling and grain weight of crop. Cytokinin (CTK) can effectively increase chlorophyll content and chloroplast stability, but it is irreversibly inactivated by cytokinin oxidase (CKX). In this study, therefore, twenty-four pairs of primers were designed to identify variations of wheat CKX (Tackx) genes associated with flag leaf chlorophyll content after anthesis, as well as grain weight in 169 recombinant inbred lines (RIL) derived from Triticum aestivum Jing 411 × Hongmangchun 21. Results indicated variation of Tackx4, identified by primer pair T19-20, was proven to significantly associate with chlorophyll content and grain weight in the RIL population. Here, two Tackx4 patterns were identified: one with two co-segregated fragments (Tackx4-1/Tackx4-2) containing 618 bp and 620 bp in size (as in Jing 411), and another with no PCR product. The two genotypes were designated as genotype-A and genotype-B, respectively. Grain weight and leaf chlorophyll content at 5~15 days after anthesis (DAA) were significantly higher in genotype-A lines than those in genotype-B lines. Mapping analysis indicated Tackx4 was closely linked to Xwmc169 on chromosome 3AL, as well as co-segregated with a major quantitative trait locus (QTL) for both grain weight and chlorophyll content of flag leaf at 5~15 DAA. This QTL explained 8.9~22.3% phenotypic variations of the two traits across four cropping seasons. Among 102 wheat varieties, a third genotype of Tackx4 was found and designated as genotype-C, also having two co-segregated fragments, Tackx4-2 and Tackx4-3 (615bp). The sequences of three fragments, Tackx4-1, Tackx4-2, and Tackx4-3, showed high identity (>98%). Therefore, these fragments could be considered as different copies at Tackx4 locus on chromosome 3AL. The effect of copy number variation (CNV) of Tackx4 was further validated. In general, genotype-A contains both significantly higher grain weight and flag leaf chlorophyll content at 5~15 DAA than those in genotype-B and genotype-C, among 102 varieties under various environments.
authors.affiliation: College of Agronomy, Anhui Agricultural University; Key Laboratory of Wheat Biology and Genetic Improvement on Southern Yellow & Huai River Valley, the Ministry of Agriculture, Hefei, 230036, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chang
authors.affiliation: College of Agronomy, Anhui Agricultural University; Key Laboratory of Wheat Biology and Genetic Improvement on Southern Yellow & Huai River Valley, the Ministry of Agriculture, Hefei, 230036, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Lu
authors.affiliation: College of Agronomy, Anhui Agricultural University; Key Laboratory of Wheat Biology and Genetic Improvement on Southern Yellow & Huai River Valley, the Ministry of Agriculture, Hefei, 230036, China.
authors.forename: Hai-Ping
authors.initials: HP
authors.lastname: Zhang
authors.affiliation: College of Agronomy, Anhui Agricultural University; Key Laboratory of Wheat Biology and Genetic Improvement on Southern Yellow & Huai River Valley, the Ministry of Agriculture, Hefei, 230036, China.
authors.forename: Chuan-Xi
authors.initials: CX
authors.lastname: Ma
authors.affiliation: College of Agronomy, Anhui Agricultural University; Key Laboratory of Wheat Biology and Genetic Improvement on Southern Yellow & Huai River Valley, the Ministry of Agriculture, Hefei, 230036, China.|Department of Biology, Saint Mary's University, Halifax, NS B3H3C3, Canada.
authors.forename: Genlou
authors.initials: G
authors.lastname: Sun
mesh_terms: D001483:Base Sequence; D002734:Chlorophyll / Q000378:metabolism*; D032461:Chromosomes, Plant / Q000235:genetics; D056915:DNA Copy Number Variations; D008040:Genetic Linkage; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D017421:Sequence Analysis; D014908:Triticum / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D002734:Chlorophyll; D010088:Oxidoreductases; C019984:cytokinin oxidase