Different sets of TaCKX genes affect yield-related traits in wheat plants grown in a controlled environment and in field conditions

Abstract

Background TaCKX wheat gene family members (GFMs) encode the enzyme cytokinin oxidase/dehydrogenase (CKX), which irreversibly degrades cytokinins. The genes are important regulators of cytokinin content and take part in growth and development, with a major impact on yield-related traits. The goal of this research was to test whether these genes might be differentially expressed in the field compared to laboratory conditions and consequently differently affect plant development and yield. Results We compared expression and crosstalk of the TaCKX GFMs and TaNAC2-5A gene in modern varieties grown in a growth chamber (GC) and in the field and looked for differences in their impact on yield-related traits. The TaNAC2-5A gene was included in the research since it was expected to play an important role in co-regulation of these genes. The range of relative expression levels of TaCKX GFMs and TaNAC2-5A gene among tested cultivars was from 5 for TaCKX8 to more than 100 for TaCKX9 in the GC and from 6 for TaCKX8 to 275 for TaCKX10 in the field. The range was similar for four of them in the GC, but was much higher for seven others and TaNAC2-5A in the field. The TaCKX GFMs and TaNAC2-5A form co-expression groups, which differ depending on growth conditions. Consequently, the genes also differently regulate yield-related traits in the GC and in the field. TaNAC2-5A took part in negative regulation of tiller number and CKX activity in seedling roots only in controlled GC conditions. Grain number and grain yield were negatively regulated by TaCKX10 in the GC but positively by TaCKX8 and others in the field. Some of the genes, which were expressed in seedling roots, negatively influenced tiller number and positively regulated seedling root weight, CKX activity in the spikes, thousand grain weight (TGW) as well as formation of semi-empty spikes. Conclusions We have documented that: 1) natural variation in expression levels of tested genes in both environments is very high, indicating the possibility of selection of beneficial genotypes for breeding purposes, 2) to create a model of an ideotype for breeding, we need to take into consideration the natural environment.

The soybean (Glycine maxL.) cytokinin oxidase/dehydrogenase multigene family; identification of natural variations for altered cytokinin content and seed yield

“…Therefore, in our work, the SNPs identified in the 4 high-yield soybean cultivars can conceivably diminish the activity of GmCKX14, and thereby enhance CK accumulation during the reproductive stages. This, would thus delay senescence, enhance photosynthesis and primordia formation, which, in turn, can increase the spike number, flower number and size, pod number, seed number and seed weight (Jameson and Song 2016;He et al 2018;Panda et al 2018;Szala et al 2020). Taken together, our data support the hypothesis that the substitution in GmCKX14 is closely linked to seed yield in soybean.…”

“…In plant species, CKX enzymes are produced by multi-gene families. Recently, progress has been made in identifying the mechanism of CKX gene family members (GFMs) to improve seed grain yield in several important crops, such as rice ( Oryza sativa L.) (Gao et al 2014; Gao et al 2019; Mao et al 2020), barley ( Hordeum vulgare L.) (Zalewski et al 2014; Holubová et al 2018; Gasparis et al 2019), and wheat ( Triticum aestivum L.) (Zhang et al 2012; Lu et al 2015; Chang et al 2015; Chen et al 2020), making CKX an emerging genetic target for crop yield improvement (Jameson and Song 2016; Szala et al 2020; Chen et al 2020). Considering the potential of CKX genes, Le et al (2012) identified and characterized expression of soybean CKX s at various plant development stages.…”

TaCKX2.2 Genes Coordinate Expression of Other TaCKX Family Members, Regulate Phytohormone Content and Yield-Related Traits of Wheat

“…This is a possible reason for the weak progress in research on bread wheat compared to other cereals. TaCKX1, TaCKX2.2.1 and TaCKX2.2.2 are mainly expressed in developing spikes, TaCKX3 and TaCKX10 in seedling roots, TaCKX5, TaCKX9 and TaCKX8 in younger organs of developing plants from seedling roots to 0 days after pollination (DAP) spikes, and TaCKX11 and TaCKX4 in all organs [32,33]. Similar tissue specificity of expression of TaCKX GFMs was presented based on RNA-seq data [12], as well as for TaCKX1 and TaCKX2 during early kernel development [13].…”

The soybean (Glycine max L.) cytokinin oxidase/dehydrogenase multigene family; Identification of natural variations for altered cytokinin content and seed yield

“…Therefore, in our work, the SNPs identified in the four high‐yield soybean cultivars can conceivably diminish the activity of GmCKX7‐1 , and thereby enhance CK accumulation during the reproductive stages. This, would thus delay senescence, enhance photosynthesis, and primordia formation, which, in turn, can increase the spike number, flower number and size, pod number, seed number and seed weight (He et al., 2018; Jameson & Song, 2016; Panda et al., 2018; Szala et al., 2020). Taken together, our data support the hypothesis that the substitution in GmCKX7‐1 is closely linked to seed yield in soybean.…”

“…In plants, CKX enzymes are produced by multi‐gene families. Recently, progress has been made in identifying the mechanism of CKX gene family members (GFMs) to improve seed grain yield in several important crops, such as rice ( Oryza sativa L.) (Gao et al., 2014, 2019; Mao et al., 2020), barley ( Hordeum vulgare L.) (Gasparis et al., 2019; Holubová et al., 2018; Zalewski et al., 2014), and wheat ( Triticum aestivum L.) (Chang et al., 2015; Chen et al., 2020; Lu et al., 2015; Zhang et al., 2012), making CKX an emerging genetic target for crop yield improvement (Chen et al., 2020; Jameson & Song, 2016; Szala et al., 2020). Considering the potential of CKX genes, Le et al.…”