Evaluation of differential qPE9-1/DEP1 protein domains in rice grain length and weight variation

BACKGROUND: qPE9–1/DEP1, encoding a G protein γ subunit, has multiple effects on plant architecture, grain size, and yield in rice. The qPE9–1 protein contains an N-terminal G gamma-like (GGL) domain, a putative transmembrane domain, and a C-terminal cysteine-rich domain. However, the roles of each domain remain unclear. RESULTS: In the present study, we focused on the genetic effects of different domains of qPE9–1 in the regulation of grain length and weight. We generated a series of transgenic plants expressing different truncated qPE9–1 proteins through constitutive expression and clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9 strategies. Phenotypic analysis indicated that the complete or long-tailed qPE9–1 contributed to the elongation of grains, while the GGL domain alone and short-tailed qPE9–1 led to short grains. The long C-terminus of qPE9–1 including two or three C-terminal von Willebrand factor type C domains effectively repressed the negative effects of the GGL domain on grain length and weight. qPE9–1-overexpressing lines in a Wuxianggeng 9 (carrying a qpe9–1 allele) background showed increased grain yield per plant, but lodging occurred in some years. CONCLUSIONS: Manipulation of the C-terminal length of qPE9–1 through genetic engineering can be used to generate varieties with various grain lengths and weights according to different requirements in rice breeding. The genetic effects of qPE9–1/qpe9–1 are multidimensional, and breeders should take into account other factors including genetic backgrounds and planting conditions in the use of qPE9–1/qpe9–1. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12284-019-0263-4) contains supplementary material, which is available to authorized users.