Virus-Induced Gene Silencing Identifies an Important Role of the TaRSR1 Transcription Factor in Starch Synthesis in Bread Wheat

Abstract

The function of a wheat starch regulator 1 (TaRSR1) in regulating the synthesis of grain storage starch was determined using the barley stripe mosaic virus—virus induced gene-silencing (BSMV-VIGS) method in field experiments. Chlorotic stripes appeared on the wheat spikes infected with barley stripe mosaic virus-virus induced gene-silencing- wheat starch regulator 1 (BSMV-VIGS-TaRSR1) at 15 days after anthesis, at which time the transcription levels of the TaRSR1 gene significantly decreased. Quantitative real-time PCR was also used to measure the transcription levels of 26 starch synthesis-related enzyme genes in the grains of BSMV-VIGS-TaRSR1-silenced wheat plants at 20, 27, and 31 days after anthesis. The results showed that the transcription levels of some starch synthesis-related enzyme genes were markedly induced at different sampling time points: TaSSI, TaSSIV, TaBEIII, TaISA1, TaISA3, TaPHOL, and TaDPE1 genes were induced at each of the three sampling time points and TaAGPS1-b, TaAGPL1, TaAGPL2, TaSSIIb, TaSSIIc, TaSSIIIb, TaBEI, TaBEIIa, TaBEIIb, TaISA2, TaPHOH, and TaDPE2 genes were induced at one sampling time point. Moreover, both the grain starch contents, one thousand kernel weights, grain length and width of BSMV-VIGS-TaRSR1-infected wheat plants significantly increased. These results suggest that TaRSR1 acts as a negative regulator and plays an important role in starch synthesis in wheat grains by temporally regulating the expression of specific starch synthesis-related enzyme genes.

Besides and Beyond Flowering: Other Roles of euAP2 Genes in Plant Development

“…In similar studies, about the same time, two groups reported that AtAP2 influenced seed shape, size, mass, content and yield in Arabidopsis [39,40]. Seeds of ap2 mutant plants were larger in size and had more weight compared to wild type seeds.…”

“…Triticum aestivum RICE STARCH REGULATOR 1 (TaRSR1) an orthologue of RSR1 has also been reported to negatively regulate a group of important starch synthesis related genes during endosperm development in wheat [35]. In another study, Liu et al (2016) [36], used barley stripe mosaic virus-virus induced gene-silencing (BSMV-VIGS) to silence TaRSR1. Their results confirmed that TaRSR1 negatively regulates critical starch synthesis related genes in wheat endosperm.…”

Besides and beyond Flowering: Other Roles of EuAP2 Genes in Plant Development

“…The histological basis of increased grain length in ssh1 was due to increased cell size and not increase in cell number. Similarly, wheat grain length and weight increased in test plants relative to control by barley stripe mosaic virus-virus-induced gene-silencing (BSMV-VIGS) of wheat starch regulator 1 (TaRSR1) [93]. Wheat grain morphology is also controlled by Q, a major domestication gene [94].…”

Besides and Beyond Flowering: Other Roles of euAP2 Genes in Plant Development

“…The histological basis of increased grain length in ssh1 was due to increased cell size and not increase in cell number. Similarly, wheat grain length and weight increased in test plants relative to control by barley stripe mosaic virus-virus induced gene-silencing (BSMV-VIGS) of wheat starch regulator 1 (TaRSR1) [90]. Wheat grain morphology is also controlled by Q, a major domestication gene [91].…”

“…Therefore, the effects of euAP2 genes on grain filling appears to differ between rice and wheat. Curiously, rice and wheat RSR1 have been functionally characterized as negative regulators of a subset of starch synthesis related genes that are highly expressed in the endosperm [87,90]. So it is rather interesting that Q does not inhibit starch synthesis in wheat.…”