iTRAQ-based proteome profile analysis of superior and inferior Spikelets at early grain filling stage in japonica Rice

Abstract

BackgroundLarge-panicle rice varieties often fail to achieve their yield potential due to poor grain filling of late-flowering inferior spikelets (IS). The physiological and molecular mechanisms of poor IS grain filling, and whether an increase in assimilate supply could regulate protein abundance and consequently improve IS grain filling for japonica rice with large panicles is still partially understood.ResultsA field experiment was performed with two spikelet removal treatments at anthesis in the large-panicle japonica rice line W1844, including removal of the top 1/3 of spikelets (T1) and removal of the top 2/3 of spikelets (T2), with no spikelet removal as a control (T0). The size, weight, setting rate, and grain filling rate of IS were significantly increased after spikelet removing. The biological functions of the differentially expressed proteins (DEPs) between superior and inferior spikelets as well as the response of IS to the removal of superior spikelets (SS) were investigated by using iTRAQ at 10 days post anthesis. A total of 159, 87, and 28 DEPs were identified from group A (T0-SS/T0-IS), group B (T0-SS/T2-IS), and group C (T2-IS/T0-IS), respectively. Among these, 104, 63, and 22 proteins were up-regulated, and 55, 24, and 6 proteins were down-regulated, respectively. Approximately half of these DEPs were involved in carbohydrate metabolism (sucrose-to-starch metabolism and energy metabolism) and protein metabolism (protein synthesis, folding, degradation, and storage).ConclusionsReduced endosperm cell division and decreased activities of key enzymes associated with sucrose-starch metabolism and nitrogen metabolism are mainly attributed to the poor sink strength of IS. In addition, due to weakened photosynthesis and respiration, IS are unable to obtain a timely supply of materials and energy after fertilization, which might be resulted in the stagnation of IS development. Finally, an increased abundance of 14–3-3 protein in IS could be involved in the inhibition of starch synthesis. The removal of SS contributed to transfer of assimilates to IS and enhanced enzymatic activities of carbon metabolism (sucrose synthase, starch branching enzyme, soluble starch synthase, and pullulanase) and nitrogen metabolism (aspartate amino transferase and alanine amino transferase), promoting starch and protein synthesis in IS. In addition, improvements in energy metabolism (greater abundance of pyrophosphate-fructose 6-phosphate 1-phosphotransferase) might be played a vital role in inducing the initiation of grain filling. These results collectively demonstrate that carbohydrate supply is the main cause of poor IS grain filling.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-017-1050-2) contains supplementary material, which is available to authorized users.

Non-Structural Carbohydrates Accumulation in Contrasting Rice Genotypes Subjected to High Night Temperatures

“…Different reports indicate the role of enzymes such as α-amilase, AGPase, BE, SSS, GBSS, plastidial FBPase, and sucrose synthase, i.e. Susy and Susase in the accumulation and remobilization of NSC in rice (Fu et al, 2011;Ishimaru et al, 2004;You et al, 2017). Considering the complexities o stem NSC dynamics and the underlying events culminating to carbohydrate allocation and its utilization, lead us to think that in the future, NSCs oscillation probably will be serve as proxy for sink strength selection criterion rather than a direct target for breeding under climate change scenarios.…”

“…Moreover, when photosynthesis reductions are accelerated leaf senescence is faster, decreasing the sucrose-starch conversion via enzymatic activity and consequently reducing the grain yield and the quality Chaturvedi et al, 2017;You et al, 2017). Considering that starch represents 80-90% of final grain weight, the events involving since grain filling and final yield are associated to assimilates supplied by current photosynthesis and stem NSC remobilization capacity (Yoshida, 1981).…”

Comparison of the chemical and textural properties of germ‐remaining soft rice grains from different spikelet positions

“…In China, due to the development of hybrid and new planttype rice varieties with a prominent feature of large spikes, poor filling of inferior grain is widespread. Different scholars have studied rice filling mechanism from the viewpoint of heredity (Wang et al, , 2009Zhao et al, 2016), physiology (Yang et al, 2000), and proteomics (You et al, 2017), and the results indicate that there is a genetic physiological basis of preferential filling and full filling in the inferior grains. Therefore, for varieties with differences in superior and inferior grain filling, reasonable water and fertilizer management and other measures should be adopted, to promote the development of inferior grain in a suitable environment.…”

Regulation of gene expression involved in the remobilization of rice straw carbon reserves results from moderate soil drying during grain filling

“…Proteomic investigations on differences in grain filling between superior grains and inferior grains (Chen et al , ; Zhu et al , ; You et al , ) and on straw reserve remobilization in wheat and rice have been conducted by using iTRAQ, 2D gel electrophoresis and the recently developed SWATH‐MS (sequential window acquisition of all theoretical mass spectra‐mass spectrometry) (Bazargani et al , ; Li et al , ). SWATH‐MS is a more promising and popular quantitative approach for protein identification and verification, which can provide more accurate quantification and large‐scale identification of differentially expressed proteins, than 2D gel electrophoresis and iTRAQ and is widely used for microbial, human, and animal systems (Liu et al , ; Liu et al , ).…”