TaHAL3-7A increases grain yield by enhancing photosynthetic pigment content in wheat (Triticum aestivum L.)

Abstract

Halotolerance 3 (HAL3) is known for its roles in salt tolerance, cell-cycle control, and cell wall integrity. However, its impact on photosynthesis- and yield-related traits in wheat (Triticum aestivum L.) remains unclear. In this study, we identified TaHAL3 genes expressed in all wheat tissues, with higher levels in wheat shoots and grains. Haplotype analysis revealed that TaHAL3-7A haplotypes were associated with flag leaf length and photosynthetic pigment content (chlorophyll a/b and carotenoid). Overexpressing TaHAL3-7A in rice and wheat significantly increased pigment levels, enhancing grain number per spike and yield per plant, while TaHAL3-7A mutants exhibited reduced pigment contents and yield-related traits. Regional experiments showed increases in grain number per spike, thousand-grain weight, and yield per plot. Transcriptomic and qPCR analyses revealed that TaHAL3-7A enhanced photosynthesis-related traits by upregulating light-harvesting chlorophyll a/b-binding (LHC) genes. Additionally, we demonstrated the physical interaction between TaHAL3-7A and TaUFD1-3A, along with their coordinated expression changes. The TaUFD1-3A mutants exhibited significant reductions in pigment content, while TaUFD1-3A-Hapl I displayed higher pigment levels and grain yield. Notably, the combination of TaUFD1-3A-Hapl I and TaHAL3-7A-Hapl I further increased chlorophyll content, thousand-grain weight, and yield per plant. These findings highlight the crucial role of TaHAL3-7A in regulating wheat photosynthetic pigments and its potential application in improving wheat yield through molecular breeding.