Spermidine Increases the Sucrose Content in Inferior Grain of Wheat and Thereby Promotes Its Grain Filling.

Jian Luo,Yang Liu,Yuncheng Liao,Juan Han,Bin Wei

doi:10.3389/fpls.2019.01309

Jian Luo, Yang Liu + Show 3 more

Open Access

https://doi.org/10.3389/fpls.2019.01309

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Abstract

The improvement of grain filling is the key issue for promoting wheat thousand grain weight and grain yield. The levels of polyamines (PAs) significantly affect grain filling in cereals, but the mechanism by which PAs affect grain filling in wheat is unclear. In the present study, six wheat cultivars whose grain filling differed were used, and their grain-filling characteristics and endogenous PA contents were measured. In addition, exogenous PAs were supplied during the wheat grain-filling period. The grain-filling characteristics, hormone levels, starch contents, and gene expression [based on RNA sequencing (RNA-seq)] in the grain were analyzed. The objective of the present study was to investigate the effects of PAs on grain filling in wheat. The results suggested that the direct synthetic pathway from putrescine (Put) to spermidine (Spd) in the grain was a key factor in promoting grain filling and thousand grain weight in wheat. Spd through regulates the grain-filling rate of inferior grain during the early grain-filling period to affecting the grain filling and thousand grain weight of wheat. The promotive effect of Spd on the grain filling of inferior wheat grain was notably related to carbohydrate metabolism in that grain. Spd significantly increased the zeatin (Z) + zeatin riboside (ZR) contents but reduced the ethylene (ETH) evolution rate in the inferior grain. In addition, Spd significantly increased the sucrose synthase (SS) and acid invertase (AI) activities in the inferior grain. These effects of Spd led to increased sucrose content in the inferior grain. These reasons might explain why Spd significantly promoted the filling and weight of inferior wheat grain.

Highlights

Wheat (Triticum aestivum L.) is an important global cereal crop species worldwide, including within China, and promoting wheat grain production is essential for food security in China
The mean grain-filling rate and thousand grain weight among the cultivars followed the order of Shuangda 1 (SD 1) > Fugao 1 (FG 1) and Zhoumai 22 (ZM 22) > Xiaoyan 6 (XY 6), Xiaoyan 22 (XY 22), and Xinong 538 (XN 538) (Figures 1A, B-a)
The active grain-filling period of the inferior grain was significantly lower than that of the superior grain in 2015–2016. These results suggested that compared with the superior grain, the significant low grain weight of inferior grain for these six cultivars seems due to the lower level of grain filling rate

Summary

Introduction

Wheat (Triticum aestivum L.) is an important global cereal crop species worldwide, including within China, and promoting wheat grain production is essential for food security in China. The grain yield of wheat can be divided into three components: the number of spikes per unit area, the number of spikelets per spike, and thousand grain weight (Yu, 2011). In China, high wheat grain yield relies mainly on high numbers of spikes per unit area (Cai et al, 2014). The high numbers of spikes may lead to severe problems, such as lodging, premature senescence, and increased damage from disease and insects (Sicher and Bunce, 1998; Robert., 2002; Kelbert et al, 2004). Increasing the thousand grain weight or grain number per spike based on a suitable panicle number per area is an inevitable approach to promote wheat grain yield.

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