Cytokinin-Regulated Sucrose Metabolism in Stay-Green Wheat Phenotype.

Wenqiang Wang,Wei Wang,Qinxue Li,Fengxia Tian,Qunqun Hao,Wujun Ma

doi:10.1371/journal.pone.0161351

Abstract

A wheat stay-green mutant, tasg1, was observed to exhibit significantly delayed senescence in the late developmental stage. The photosynthetic capacity of the flag leaf was greater in tasg1 than in wild type (WT) plants. In addition, the grain volume of tasg1 was significantly higher than that of WT at the early filling stage. The content of various cytokinins (CKs) in the grain was significantly higher in tasg1 than in WT and was accompanied by an upregulated expression of some cell cycle-related genes. Examination of the metabolism of soluble sugars in tasg1 and WT revealed that the concentrations of glucose (Glu), fructose (Fru), and sucrose (Suc) were higher in the flag leaves and grains of tasg1 than in WT plants. The activities of sucrose-phosphate synthase (SPS), sucrose synthase (SuSy), and cell wall invertase (CW-invertase) were higher in tasg1, suggesting an altered metabolism and transport of soluble sugars. Furthermore, when tasg1 was treated with the CK inhibitor lovastatin, the activity of invertase was inhibited and was associated with premature senescence phenotype. However, the activity of invertase was partially recovered in tasg1 when treated with 6-benzylaminopurine (BAP). The trend of change in the concentrations of Glu, Fru, and Suc was similar to that of invertase. Our results suggest that CKs might regulate the stay-green phenotype of tasg1 by regulating the invertase activity involved in Suc remobilization.

Highlights

Senescence is an internally programmed degenerative process leading to death in plants
The grain length was longer in tasg1 than in wild type (WT) (Fig 1C), but there was no obvious difference in the grain width between tasg1 and WT (Fig 1D)
The expression of cyclin D2 (CycD2, G1 phase) was increased at the early filling stage (Fig 4D), and it was higher in tasg1 than in WT. These results suggest that the expression of CDKB and CycD2 might play an important role in increasing the grain volume in tasg1 compared to WT at the early filling stage

Summary

Introduction

Senescence is an internally programmed degenerative process leading to death in plants. Compared to wild type (WT) plants, stay-green or non-yellowing mutants of various plant species have been reported to maintain leaf greenness for longer time during senescence and are ideal materials for studying the mechanisms underlying plant senescence. Some stay-green mutants maintain photosynthetic activity for longer durations and are, expected to have a higher yield [1, 2]. The mechanisms underlying the stay-green or delayed senescence phenotype remain unclear, to date. Cytokinins (CKs) are known to play important roles in plant growth and developmental processes, including senescence [3]. These processes are linked to the demand for PLOS ONE | DOI:10.1371/journal.pone.0161351. These processes are linked to the demand for PLOS ONE | DOI:10.1371/journal.pone.0161351 August 31, 2016

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