Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
Howard Hughes Medical Institute, Chevy Chase, MD, 20815, USA.
Theor Appl Genet. 2023 Oct 31;136(11):237. doi: 10.1007/s00122-023-04484-x.
The wheat transcription factor bZIPC1 interacts with FT2 and affects spikelet and grain number per spike. We identified a natural allele with positive effects on these two economically important traits. Loss-of-function mutations and natural variation in the gene FLOWERING LOCUS T2 (FT2) in wheat have previously been shown to affect spikelet number per spike (SNS). However, while other FT-like wheat proteins interact with bZIP-containing transcription factors from the A-group, FT2 does not interact with any of them. In this study, we used a yeast-two-hybrid screen with FT2 as bait and identified a grass-specific bZIP-containing transcription factor from the C-group, designated here as bZIPC1. Within the C-group, we identified four clades including wheat proteins that show Y2H interactions with different sets of FT-like and CEN-like encoded proteins. bZIPC1 and FT2 expression partially overlap in the developing spike, including the inflorescence meristem. Combined loss-of-function mutations in bZIPC-A1 and bZIPC-B1 (bzipc1) in tetraploid wheat resulted in a drastic reduction in SNS with a limited effect on heading date. Analysis of natural variation in the bZIPC-B1 (TraesCS5B02G444100) region revealed three major haplotypes (H1-H3), with the H1 haplotype showing significantly higher SNS, grain number per spike and grain weight per spike than both the H2 and H3 haplotypes. The favorable effect of the H1 haplotype was also supported by its increased frequency from the ancestral cultivated tetraploids to the modern tetraploid and hexaploid wheat varieties. We developed markers for the two non-synonymous SNPs that differentiate the bZIPC-B1b allele in the H1 haplotype from the ancestral bZIPC-B1a allele present in all other haplotypes. These diagnostic markers are useful tools to accelerate the deployment of the favorable bZIPC-B1b allele in pasta and bread wheat breeding programs.
小麦转录因子 bZIPC1 与 FT2 相互作用，影响小穗和每穗粒数。我们鉴定了一个对这两个具有重要经济意义的性状具有正向影响的自然等位基因。先前的研究表明，小麦 FLOWERING LOCUS T2（FT2）基因的功能丧失突变和自然变异会影响每穗小穗数（SNS）。然而，虽然其他 FT 样小麦蛋白与 A 组含 bZIP 的转录因子相互作用，但 FT2 与它们中的任何一个都不相互作用。在这项研究中，我们使用了以 FT2 为诱饵的酵母双杂交筛选，鉴定了一个来自 C 组的草特异性含 bZIP 的转录因子，我们将其命名为 bZIPC1。在 C 组内，我们鉴定了四个分支，包括与不同的 FT 样和 CEN 样编码蛋白有 Y2H 相互作用的小麦蛋白。bZIPC1 和 FT2 的表达在发育中的小穗中部分重叠，包括花序分生组织。在四倍体小麦中，bZIPC-A1 和 bZIPC-B1（bzipc1）的功能丧失突变的组合导致 SNS 急剧减少，而对抽穗期的影响有限。对 bZIPC-B1（TraesCS5B02G444100）区域自然变异的分析表明存在三个主要的单倍型（H1-H3），与 H2 和 H3 单倍型相比，H1 单倍型的 SNS、每穗粒数和每穗粒重显著更高。H1 单倍型的有利影响也得到了支持，因为它从原始栽培四倍体到现代四倍体和六倍体小麦品种的频率增加。我们开发了两个非同义 SNP 的标记，这些 SNP 可区分 H1 单倍型中 bZIPC-B1b 等位基因与存在于所有其他单倍型中的原始 bZIPC-B1a 等位基因。这些诊断标记是在面食和面包小麦育种计划中加速有利 bZIPC-B1b 等位基因部署的有用工具。
