Copy Number Variation of Cytokinin Oxidase Gene <i>Tackx4 </i>Associated with Grain Weight and Chlorophyll Content of Flag Leaf in Common Wheat


<div><p>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 (<i>Tackx</i>) genes associated with flag leaf chlorophyll content after anthesis, as well as grain weight in 169 recombinant inbred lines (RIL) derived from <i>Triticum aestivum</i> Jing 411 × Hongmangchun 21. Results indicated variation of <i>Tackx4</i>, identified by primer pair T19-20, was proven to significantly associate with chlorophyll content and grain weight in the RIL population. Here, two <i>Tackx4</i> patterns were identified: one with two co-segregated fragments (<i>Tackx4-1</i>/<i>Tackx4-2</i>) 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 <i>Tackx4</i> was closely linked to <i>Xwmc169</i> 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 <i>Tackx4</i> was found and designated as genotype-C, also having two co-segregated fragments, <i>Tackx4-2</i> and <i>Tackx4-3</i> (615bp). The sequences of three fragments, <i>Tackx4-1</i>, <i>Tackx4-2</i>, and <i>Tackx4-3</i>, showed high identity (>98%). Therefore, these fragments could be considered as different copies at <i>Tackx4</i> locus on chromosome 3AL. The effect of copy number variation (CNV) of <i>Tackx4</i> 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.</p></div

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oai:figshare.com:article/1631003Last time updated on 2/12/2018

This paper was published in FigShare.

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