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. 2016 Aug 5:7:1161.
doi: 10.3389/fpls.2016.01161. eCollection 2016.

Effect of Removing Superior Spikelets on Grain Filling of Inferior Spikelets in Rice

Cuicui You  1 , Honglei Zhu  1 , Beibei Xu  1 , Wenxiao Huang  1 , Shaohua Wang  1 , Yanfeng Ding  2 , Zhenghui Liu  2 , Ganghua Li  1 , Lin Chen  1 , Chengqiang Ding  1 , She Tang  1
Affiliations

Effect of Removing Superior Spikelets on Grain Filling of Inferior Spikelets in Rice

Cuicui You et al. Front Plant Sci. .

Abstract

Large-panicle rice cultivars often fail to reach their yield potential due to the poor grain filling of inferior spikelets (IS). Thus, it is important to determine the causes of poor IS grain filling. In this study, we attempted to identify whether inferior grain filling of large panicles is restricted by superior spikelets (SS) and their physiological mechanism. SS were removed from two homozygous japonica rice strains (W1844 and WJ165) during flowering in an attempt to force photosynthate transport to the IS. We measured the effects of SS removal on seed setting rate, grain weight, grain filling rate, sucrose content, as well as hormone levels, activities of key enzymes, and expression of genes involved in sucrose to starch metabolism in rice IS during grain filling. The results showed that SS removal improved IS grain filling by increasing the seed setting rate, grain weight, sucrose content, and hormone levels. SS removal also enhanced the activities of key enzymes and the expression levels of genes involved in sucrose to starch metabolism. These results suggest that sucrose and several hormones act as signal substances and play a vital role in grain filling by regulating enzyme activities and gene expression. Therefore, IS grain filling is restricted by SS, which limit assimilate supply and plant hormones, leading to poor grain filling of IS.

Keywords: enzyme activity; grain filling; inferior spikelets; plant hormones; rice; sucrose to starch metabolism; superior spikelet removal.

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Figures

FIGURE 1
FIGURE 1
Sucrose content of SS and IS of rice during grain filling. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 2
FIGURE 2
Grain weight of SS and IS of rice during grain filling. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 3
FIGURE 3
Grain filling rate of SS and IS of rice during grain filling. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed.
FIGURE 4
FIGURE 4
Hormones content (ZR, IAA, and ABA) of SS and IS during the grain filling period of rice. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 5
FIGURE 5
Activities of key enzymes involved in sucrose to starch conversion in SS and IS during the grain filling period of rice. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 6
FIGURE 6
Relative mRNA level of SuS2, SuS3, and SuS4 in SS and IS during the grain filling period of rice. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 7
FIGURE 7
Relative mRNA level of AGPS2, AGPL1, and AGPL2 in SS and IS during the grain filling period of rice. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 8
FIGURE 8
Relative mRNA level of SSSI, SSSII-3, and SSSIII-2 in SS and IS during the grain filling period of rice. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
FIGURE 9
FIGURE 9
Relative mRNA level of SBEI, SBEIII, and SBEIV in SS and IS during the grain filling period of rice. T0 and T2 represent control group without any treatment and top 2/3 of the spikelets were removed. Vertical bars represent mean values ± SE (n = 3).
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