Evaluation of the effects of mutation in the wheat AP2 homoeologs on the potential for cleistogamous flowering

Nanape, Bigie Agetha

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Evaluation of the effects of mutation in the wheat AP2 homoeologs on the potential for cleistogamous flowering

http://hdl.handle.net/10076/0002000889

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2024DB0702.pdf (4.5 MB)

Item type

学位論文 / Thesis or Dissertation(1)

公開日

2024-09-25

タイトル

Evaluation of the effects of mutation in the wheat AP2 homoeologs on the potential for cleistogamous flowering

言語

eng

資源タイプ

資源タイプ識別子

http://purl.org/coar/resource_type/c_db06

資源タイプ

doctoral thesis

アクセス権

open access

アクセス権URI

http://purl.org/coar/access_right/c_abf2

著者

Nanape, Bigie Agetha

著者（ヨミ）

姓名

ナナぺ, ビギーアゲサ

言語

ja-Kana

抄録

内容記述タイプ

Abstract

内容記述

Cleistogamy or fertilization in closed flowers reduces the risk of fungal infection of the florets at anthesis in Triticeae crops. Cleistogamy in barley (Hordeum vulgare) is determined by a single recessive gene at the Cleistogamy1 (Cly1) locus on chromosome 2H. The Cly1 gene is known to be the barley ortholog of the Arabidopsis Apetala2 (AP2) transcription factor gene. A point mutation within the microRNA172 (miR172) target site of Cly1 inhibits the binding of miR172 to the target site of the mRNA, resulting in the production of the Cly1 (HvAP2) protein. This protein negatively regulates the development of lodicules, keeping florets closed at anthesis. However, cleistogamy is not evident in hexaploid wheat (Triticum aestivum) cultivars. The aim of this study is to develop a cleistogamous wheat which could evade the infection caused by Fusarium head blight and to minimize pollen-mediated gene flow. The present study focused on evaluating the effects of mutations in the wheat AP2 homoeologs on the potential for cleistogamous flowering.
The initial objective was to identify newly induced mutations in the wheat AP2 homoeologs, the three homoeologous genes (AP2-A, AP2-B and AP2-D) located on chromosomes 2A, 2B and 2D. The AP2 mutants were induced from the Japanese winter wheat cultivar 'Kitahonami' by ethyl methanesulfonate (EMS) treatment of the seeds. Three independent mutants carrying novel point mutations within the miR172 target site in AP2-A and AP2-D were identified and the mutant alleles were designated as AP2-A1, AP2-D1 and AP2-D2. However, no point mutations within the miR172 target site were detected in AP2-B. These point mutations were distinct from those identified in the cleistogamous alleles cly1.b and cly1.c of the orthologous barley Cly1 gene. Field observations showed normal flowering in all mutants. The lodicules of the mutants swelled during anthesis, however, their sizes exhibited notable variations compared to the wild type. Lodicule depth was decreased in all three mutants, with AP2-D2 exhibiting the greatest reduction. Lodicule length and width showed a similar trend in AP2-D2, however, not in AP2-A1 or AP2-D1. Furthermore, AP2-D2 had much shorter (compact) spikes compared to AP2-A1 and AP2-D1. The reduced spike length was due to a significant reduction in the length of the rachis (spike) internode. Reduced interaction between mRNA and miR172 at the target site of AP2-D2 resulted in higher transcript levels that suppressed lodicule development and rachis internode elongation.
A proposed strategy to develop cleistogamous wheat is to accumulate the point mutations in all three AP2 homoeologs. This study provided insights into the cumulative effects of mutant AP2 alleles in suppressing open flowering. A precise evaluation of the effects of the mutations was made using near-isogenic lines (NILs). Three single mutants (AP2-A1, AP2-D1 and AP2-D2) with two double mutants (AP2-A1/AP2-D1 and AP2- A1/AP2-D2) were evaluated for the effects on flowering and other agronomic traits under near-isogenic background. Among the three single mutant alleles, AP2-D2 had the greatest effect on reducing the rate of anther extrusion. Furthermore, the double mutant AP2-A1/AP2-D2 inhibited anther extrusion more than the single mutant AP2-D2. Similarly, AP2-D2 had the greatest effect on reducing lodicule depth, whereas AP2- A1/AP2-D2 showed a significantly greater reduction in lodicule depth than AP2-D2. AP2-D2 had an additive effect on reducing rachis (spike) internode length, although both AP2-A1 and AP2-D1 also had an effect, but less than AP2-D2. The double mutant AP2- A1/AP2-D1 had a stronger effect on reducing rachis internode length than either AP2-A1 or AP2-D1, indicating the cumulative effect of these two alleles. In addition, both single and double mutants carrying the AP2-D2 allele had shorter culm lengths due to its reduced internode length, suggesting its pleiotropic effect on stem elongation. The AP2-D2 allele showed higher expression levels than the wild type in several floral organs as well as in the rachis and culm.
In conclusion, AP2-A1/AP2-D2 was evaluated as the most effective genotype in suppressing flower opening, although cleistogamy was not achieved. The study also provided new insights into the pleiotropic effects of individual mutant AP2 alleles on plant development and agronomic traits in wheat.

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本文

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97p

書誌情報

発行日 2024-07-17

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内容記述

application/pdf

著者版フラグ

出版タイプ

VoR

出版タイプResource

http://purl.org/coar/version/c_970fb48d4fbd8a85

その他の言語のタイトル

その他のタイトル

コムギAP2 同祖遺伝子変異が閉花受粉性の獲得に及ぼす効果の評価

言語

出版者

三重大学

出版者（ヨミ）

値

ミエダイガク

学位名

博士(学術)

学位授与機関

学位授与機関識別子Scheme

kakenhi

学位授与機関識別子

14101

学位授与機関名

三重大学

学位授与年月日

2024-07-17

学位授与番号

甲学術第2276号

資源タイプ（三重大）

値

Doctoral Dissertation / 博士論文

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Evaluation of the effects of mutation in the wheat AP2 homoeologs on the potential for cleistogamous flowering

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