A Class II KNOX Gene, KNAT7-1, Regulates Physical Seed Dormancy in Mungbean [ Vigna radiata (L.) Wilczek]

Kularb Laosatit; Kitiya Amkul; Tarika Yimram; Jingbin Chen; Yun Lin; Xingxing Yuan; Lixia Wang; Xin Chen; Prakit Somta

doi:10.3389/fpls.2022.852373

A Class II KNOX Gene, KNAT7-1, Regulates Physical Seed Dormancy in Mungbean [ Vigna radiata (L.) Wilczek]

Front Plant Sci. 2022 Mar 15:13:852373. doi: 10.3389/fpls.2022.852373. eCollection 2022.

Authors

Kularb Laosatit^{1

2}, Kitiya Amkul¹, Tarika Yimram¹, Jingbin Chen³, Yun Lin³, Xingxing Yuan³, Lixia Wang⁴, Xin Chen³, Prakit Somta^{1

2

5

6}

Affiliations

¹ Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Nakhon Pathom, Thailand.
² Center for Advanced Studies for Agriculture and Food, Kasetsart University Institute for Advanced Studies, Kasetsart University, Bangkok, Thailand.
³ Institute of Industrial Crops, Jiangsu Academy of Agricultural Sciences, Nanjing, China.
⁴ Institute of Crop Sciences, Chinese Academy of Agricultural Sciences (CAAS), Beijing, China.
⁵ Center for Agricultural Biotechnology, Kasetsart University, Nakhon Pathom, Thailand.
⁶ Center of Excellence on Agricultural Biotechnology: (AG-BIO/MHESI), Bangkok, Thailand.

Abstract

Seed dormancy in wild mungbean (Vigna radiata var. sublobata) may be useful for the breeding of cultivated mungbean (var. radiata) with pre-harvest sprouting resistance. Previous studies have identified two major quantitative trait loci (QTLs) for seed dormancy, HsA and Sdwa5.1.1+, in wild mungbean that are possibly having the same locus or linked. However, these QTLs have not been confirmed/verified and a molecular basis of seed dormancy in mungbean is not yet known. In this study, we aimed to finely map the Sdwa5.1.1+ and identify candidate gene(s) for this locus. Microscopic observations revealed that wild mungbean "ACC41" seeds had a palisade cuticle layer, while cultivated mungbean "Kamphaeng Saen 2" (KPS2) seeds lacked this layer. Fine mapping using an F₂ population developed from a cross between ACC41 and KPS2 revealed two linked QTLs, Sdwa5.1.1+ and Sdwa5.1.2+, controlling seed dormancy. The Sdwa5.1.1+ was confirmed in an F_2:3 population derived from the same cross and mapped to a 3.298-Kb region containing only one gene LOC106767068, designated as VrKNAT7-1, which encodes the transcription factor KNOTTED ARABIDOPSIS THALIANA7 (KNAT7), a class II KNOTTED1-LIKE HOMEOBOX (KNOX II) protein. VrKNAX7 sequence alignment between ACC41 and KPS2 revealed several polymorphisms in the coding, untranslated, and promoter regions. Quantitative real-time PCR (qRT-PCR) analysis revealed that the expression of VrKNAT7-1 and VrCYP86A, a putative downstream regulation of VrKNAT7-1, in the seed coat of ACC41 is statistically much higher than that of KPS2. Altogether, these results indicate that VrKNAT7-1 controls physical seed dormancy in the wild mungbean ACC41.

Keywords: KNAT7; KNOX II; hardseededness; mungbean; seed dormancy.