The heterotrimeric G protein β subunit RGB1 is required for seedling formation in rice

Abstract

Background The heterotrimeric G protein β subunit RGB1 plays an important role in plant growth and development. However, the molecular mechanisms underlying the regulation of rice growth by RGB1 remain elusive. Results Here, the rgb1 mutants rgb1–1 (+ 1 bp), rgb1–2 (− 1 bp), and rgb1–3 (− 11 bp) were isolated using the CRISPR/Cas9 system, and they were arrested at 1 day after germination and ultimately exhibited seedling lethality. The dynamic anatomical characteristics of the embryos of the rgb1 seedlings and WT during early postgermination and according to TUNEL assays showed that the suppressed growth of the rgb1 mutants was caused by cell death. In addition to the limited shoot and root development, the development of the embryo shoot-root axis was suppressed in the rgb1 mutants. RGB1 was expressed mainly in the root epidermal and vascular tissues of the embryo. Moreover, transcript profiling analysis revealed that the expression of a large number of auxin-, cytokinin-, and brassinosteroid-inducible genes was upregulated or downregulated in the rgb1 mutant compared to the wild type during seedling development. Conclusions Overall, the rgb1 mutants provide an ideal material for exploring the molecular mechanism underlying rice seedling formation during early postgermination development by G proteins. Significance statement The heterotrimeric G protein β subunit RGB1 acts as a crucial factor in promoting early postgermination seedling development in rice. Electronic supplementary material The online version of this article (10.1186/s12284-019-0313-y) contains supplementary material, which is available to authorized users.

Heterotrimeric G protein are involved in the regulation of multiple agronomic traits and stress tolerance in rice

“…Our studies confirmed that the null mutants of RGA1 showed a severe dwarf phenotype and exhibited stress tolerance under drought, chilling, and salinity treatments. The suppression of RGB1 causes dwarfism and browning of the internodes and lamina joint regions [27], and the null mutant of RGB1 was lethal under the genetic background of ZH11 [31,32].…”

“…The rgb1 mutant exhibited a semi-dwarf phenotype, and the panicle number was less than that of the WT. Sun [31,32]. However, the three base and six base deletions in rgb1-1 and rgb1-2 did not cause a frame shift, which might be the reason for the survival of rgb1-1 and rgb1-2.…”

The maize heterotrimeric G-protein β subunit controls shoot meristem development and immune responses

“…They also control many important agronomic traits in cereals (16,23,30,(36)(37)(38)(39), and understanding G-protein signaling requires a study of each subunit. Rice Gb CRISPR null mutants undergo an early developmental arrest and death, but the underlying mechanism was unclear (23,24). Here, we show that maize Gb null alleles are also lethal, and this is due to autoimmunity, not to specific developmental defects.…”

“…Maize Ga (CT2) and Arabidopsis Ga and b subunits control meristem development (16,18,25). However, the role of Gb in meristem regulation in the grasses remains obscure, because rice Gb knockouts are lethal, leading to the proposal that it is essential for growth (23,24). To study the function of maize Gb, we used CRISPR/Cas9 to generate multiple alleles, including 1bp and 136-bp deletions with premature stop codons predicted to result in null alleles ( Fig.…”

“…RNAi suppression of the rice Gb gene RGB1 causes browning of internodes and ectopic cell death in roots, phenotypes associated with immune defects (21,22). However, the functions of monocot Gb genes in development have never been dissected, because CRISPR/Cas9-derived rgb1 null mutants die soon after germination (23,24).…”