Heterologous expression of ZmGS5 enhances organ size and seed weight by regulating cell expansion in Arabidopsis thaliana.

Maize ZmGS5 was reported to be positively associated with kernel-related traits, however, its regulatory mechanism on plant development and seed size remains unknown. In this study, ZmGS5 was demonstrated to be widely expressed in various maize tissues with the highest expression level in developing embryos, indicating its critical roles in early kernel development process. The ZmGS5 protein was subcellularly localized to both the nucleus and cytoplasm. Transgenic Arabidopsis plants overexpressing ZmGS5 under the control of either the constitutive maize Ubiquitin1 promotor or native ZmGS5 promoter resulted in increased plant size, biomass, seed size and weight, although no significant difference was observed between transgenic lines harboring the two constructs. In contrast, the antisense-ZmGS5 transgene resulted in opposite phenotypes. Our cytological data suggested that ZmGS5 enlarged petal size through enhancing cell expansion. Quantitative RT-PCR analysis indicated that ZmGS5 might enhance cell expansion and grain filling by upregulating expression levels of particular EXPA or SWEET genes. Collectively, these findings help us further understand the biological function and regulatory mechanism of ZmGS5 in improving organ size and seed weight, which imply its great potential for high-yield breeding in the future.
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