Overexpression of OsMYB1R1–VP64 fusion protein increases grain yield in rice by delaying flowering time

Abstract

Edited by Ulf-Ingo Fl€ ugge VP64 is widely used as a transcriptional activator to investigate the biological function of genes, but its potential for application in genetic improvement of crops has not been fully investigated. Here, we characterized an OsMYB1R1-VP64 fusion protein that enhanced the grain yield of rice cultivar 'Kita-ake' by 35%. OsMYB1R1-VP64 regulated grain yield of transgenic plants mainly by extending the vegetative growth stage. Further analysis indicated that OsMYB1R1-VP64 delayed flowering by down-regulating expression of Heading date 3a (Hd3a) and RICE FLOWERING LOCUST 1 (RFT1) through repression of Early heading date 1 (Ehd1). The expression pattern of OsMYB1R1 was constitutive and rhythmically controlled. OsMYB1R1 protein had transcriptional activation activity and was localized to the nucleus. Our findings suggest that the OsMYB1R1-VP64 construct can be used to increase grain yield in rice.Keywords: flowering time; grain yield; VP64 Rice (Oryza sativa L.) is one of the most important food crops in the world, and is the staple food for more than 75% of the population in Asia [1]. With increasing population and decreasing arable land area more productive varieties are needed to address food shortages. The yield of a rice variety is determined by three important factors, namely effective panicle number per plant, grain number per panicle, and 1000-grain weight. These in turn are affected by genotype, environmental conditions (physical environment and agronomy), and their interactions. The key genetic factors are tiller number, flowering time, fertility, and seed setting rate. As the transition point, flowering time plays a key role in coordination between vegetative and reproductive growth [2]. Vegetative growth sets the basis of reproductive growth, which involves the formation, quality, and nutritive accumulation of reproductive organs. Flowering time also affects crop yield by enabling crops to gain the maximum benefit from the prevailing conditions [3,4]. Therefore, control and optimization of flowering time has been under intense scrutiny by breeders and agronomists for a long time [5].

Transcriptional activation and phosphorylation of OsCNGC9 confer enhanced chilling tolerance in rice

“…Total RNA isolation and qRT-PCR assays were performed as previously described (Wang et al, 2016). In brief, total RNA was extracted from rice tissues using an RNeasy Plant Mini Kit (Zymo).…”

A cyclic nucleotide-gated channel mediates cytoplasmic calcium elevation and disease resistance in rice

“…The alignment was adjusted manually and the neighbor-joining tree was constructed by MEGA 4.0 (http://www.megasoftware.net/) using the bootstrap method with 1000 replicates as previously described. 52 The amino acid sequences were obtained from Rice Genome Automated Annotation System (http://ricegaas.dna.affrc.go.jp/), the Arabidopsis Information Resource (https://www.arabidopsis.org/) and the National Center for Biotechnology Information (https://www. ncbi.nlm.nih.gov/).…”

“…The RNA isolation and qRT-PCR assay were conducted as previously described. 52 Briefly, total RNA was extracted from rice tissues using a plant RNA extraction kit (Qiagen, Hilden, Germany) according to the manufacturer's instructions. For qRT-PCR, total RNA (1 μg) was reverse transcribed to cDNA using a QuantiTect Reverse Transcription Kit (Qiagen).…”

Identification of a G2-like transcription factor, OsPHL3, functions as a negative regulator of flowering in rice by co-expression and reverse genetic analysis

“…Of those genes, 21 genes were positively co-expressed and 7 genes were negatively co-expressed. Negative regulation of flowering-time genes increase grain yield of rice [ 9 , 26 , 35 , 36 ]. Therefore, to identify negative regulators of flowering time are of agricultural importance.…”

“…Until now, most of the flowering-time genes were identified by map-based cloning in mutant plants or plants with natural variations, or alternatively by overexpression and knockdown transgenic plants [ 1 ]. For example, the function of OsMADS34 [ 21 ] and OsTrx1 [ 22 ] was investigated by knockdown transgenic lines; while that of OsMADS15 [ 23 ], OsMADS50 [ 24 , 25 ], OsMADS56 [ 25 ], OsMYB1R1 [ 26 ], OsBBX14 [ 27 ] and OsCOL13 [ 28 ] was revealed by overexpression transgenic lines. Co-expression analysis in rice has been proven to be a useful tool for identifying the function of transcription factors, such as HYR in regulating the photosynthesis process and RSR1 in controlling starch biosynthesis [ 29 , 30 ].…”