Endosperm-specific overexpression of Opaque2 increases maize kernel texture
Kernel texture is a crucial trait for crop quality and utilization, yet limited genes are reported to improve texture for breeding improvement. The endosperm-filling central regulator Opaque2 (O2) coordinately and synergistically regulates starch and protein synthesis, which is highly associated with vitreous endosperm formation. In this study, we specifically overexpressed O2 in the developing endosperm to investigate the corresponding texture and quality impacts. Notably, the O2 overexpression (OE) kernels displayed enhanced test weight and 100-kernel weight, despite the kernel dimension was compromised. The kernel texture was enhanced with more vitreous endosperm region in the OE transgene. Furthermore, the sugar contents were increased in OE, including amylose, amylopectin, and starch. The starch granules were more intense in the OE endosperm with high packing pattern. The zein compounds were dramatically elevated in OE in comparison with wild type. However, the nonzein levels were slightly decreased in OE, leading to still elevated total protein accumulation. Further transcriptomic analysis comprehensively revealed that the OE kernels positively influences a series of biological processes to precisely modulate vitreous endosperm traits and texture improvement. This work provides a novel insight for maize texture improvement through specific O2 overexpression.