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

Bartosz Jablonski,Mateusz Przyborowski,Anna Nadolska-Orczyk,Sebastian Gasparis,Magdalena Chmur,Waclaw Orczyk,Karolina Szala,Andrzej Bajguz

doi:10.3390/ijms22084142

Abstract

TaCKX gene family members (GFMs) play essential roles in the regulation of cytokinin during wheat development and significantly influence yield-related traits. However, detailed function of most of them is not known. To characterize the role of TaCKX2.2 genes we silenced all homoeologous copies of both TaCKX2.2.1 and TaCKX2.2.2 by RNAi technology and observed the effect of silencing in 7 DAP spikes of T1 and T2 generations. The levels of gene silencing of these developmentally regulated genes were different in both generations, which variously determined particular phenotypes. High silencing of TaCKX2.2.2 in T2 was accompanied by slight down-regulation of TaCKX2.2.1 and strong up-regulation of TaCKX5 and TaCKX11, and expression of TaCKX1, TaCKX2.1, and TaCKX9 was comparable to the non-silenced control. Co-ordinated expression of TaCKX2.2.2 with other TaCKX GFMs influenced phytohormonal homeostasis. Contents of isoprenoid, active cytokinins, their conjugates, and auxin in seven DAP spikes of silenced T2 plants increased from 1.27 to 2.51 times. However, benzyladenine (BA) and abscisic acid (ABA) contents were significantly reduced and GA3 was not detected. We documented a significant role of TaCKX2.2.2 in the regulation of thousand grain weight (TGW), grain number, and chlorophyll content, and demonstrated the formation of a homeostatic feedback loop between the transcription of tested genes and phytohormones. We also discuss the mechanism of regulation of yield-related traits.

Highlights

Bread wheat (Triticum aestivum L.) is one of the most widely grown and economically important cereal species in the world
The silencing effect for the two was tested in T1 (Figure 1a,c) and a test for TaCKX2.1 was included in the T2 generation (Figure 1d,e)
TaCKX2.2.2 and TaCKX2.2.1 by 41% in the T1 group of plants resulted in obtaining shorter plants and slightly lower parameters of yield-related traits

Summary

Introduction

Bread wheat (Triticum aestivum L.) is one of the most widely grown and economically important cereal species in the world. This high-yielding species is comparable in production to rice and maize but contains higher protein level, and is rich in vitamins and dietary fibres [1,2]. The large and complex, allohexaploid genome of bread wheat, which is composed of three diploid genomes (AABBDD), is a great reservoir of homoeologous genes. Knowledge of their function can be applied directly or after genetic modifications in wheat breeding as reviewed previously [5]. Transformation technology used in this type of research is still a bottle-neck in the case of species with a large and complex genome

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Discussion

Conclusion