Development of high-lysine rice via endosperm-specific expression of a foreign LYSINE RICH PROTEIN gene.

Xin Liu,Samuel S M Sun,Cuicui Zhang,Xiurong Wang,Dingyang Yuan,Gang Pan,Qiaoquan Liu,Jumin Tu

doi:10.1186/s12870-016-0837-x

Xin Liu, Samuel S M Sun + Show 6 more

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https://doi.org/10.1186/s12870-016-0837-x

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Abstract

BackgroundLysine (Lys) is considered to be the first limiting essential amino acid in rice. Although there have been extensive efforts to improve the Lys content of rice through traditional breeding and genetic engineering, no satisfactory products have been achieved to date.ResultsWe expressed a LYSINE-RICH PROTEIN gene (LRP) from Psophocarpus tetragonolobus (L.) DC using an endosperm-specific GLUTELIN1 promoter (GT1) in Peiai64S (PA64S), an elite photoperiod-thermo sensitive male sterility (PTSMS) line. The expression of the foreign LRP protein was confirmed by Western blot analysis. The Lys level in the transgenic rice seeds increased more than 30 %, the total amount of other amino acids also increased compared to wild-type. Persistent investigation of amino acids in 3 generations showed that the Lys content was significantly increased in seeds of transgenic rice. Furthermore, Lys content in the hybrid of the transgenic plants also had an approximate 20 % increase compared to hybrid control. At the grain-filling stage, we monitored the transcript abundance of many genes encoding key enzymes involved in amino acid metabolism, and the results suggested that reduced amino acid catabolism led to the accumulation of amino acids in the transgenic plants. The genetically engineered rice showed unfavorable grain phenotypes compared to wild-type, however, its hybrid displayed little negative effects on grain.ConclusionsEndosperm-specific expression of foreign LRP significantly increased the Lys content in the seeds of transgenic plant, and the the Lys increase was stably heritable with 3 generation investigation. The hybrid of the transgenic plants also showed significant increases of Lys content in the seeds. These results indicated that expression of LRP in rice seeds may have promising applications in improving Lys levels in rice.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0837-x) contains supplementary material, which is available to authorized users.

Highlights

Lysine (Lys) is considered to be the first limiting essential amino acid in rice
Generation of the PA64S-derived line PA110 expressing the LYSINE-RICH PROTEIN gene (LRP) gene To improve the Lys content of rice, a binary vector carrying the LRP gene under the control of the rice endosperm-specific GLUTELIN1 promoter (GT1) and the selectable marker gene HYGROMYCIN PHOSPHOTRANSFERASE (HPT) driven by the cauliflower mosaic virus (CaMV) 35S promoter was introduced into PA64S via Agrobacterium-mediated transformation (Fig. 1a)
Western blot analysis was employed to evaluate the expression of the LRP protein in the endosperm of PA110; known concentrations of purified LRP from Psophocarpus tetragonolobus (L.) DC seeds were used as quantification references, and soluble protein extracted from wild-type PA64S was used as a negative control

Summary

Introduction

Lysine (Lys) is considered to be the first limiting essential amino acid in rice. There have been extensive efforts to improve the Lys content of rice through traditional breeding and genetic engineering, no satisfactory products have been achieved to date. The protein in rice is nutritionally incomplete due to a deficiency in essential amino acids for humans and livestock [5]. Lys is considered to be the first limiting essential amino acid in rice. A subsequent improved maize variety of the opaque genotype, quality protein maize (QPM), has been developed [8], which significantly increased the Lys level and solved the problem of the negative effects on important agronomical traits that accompany the classical

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