Department of Plant Science and Research Institute for Agriculture and Life Sciences, and Plant Genomics and Breeding Institute, Seoul National University, Seoul, 08826, South Korea.
Graduate School of Integrated Bioindustry, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul, 05006, South Korea.
Theor Appl Genet. 2018 Jul;131(7):1469-1480. doi: 10.1007/s00122-018-3091-9. Epub 2018 Mar 21.
The split-hull phenotype caused by reduced lemma width and low lignin content is under control of SPH encoding a type-2 13-lipoxygenase and contributes to high dehulling efficiency. Rice hulls consist of two bract-like structures, the lemma and palea. The hull is an important organ that helps to protect seeds from environmental stress, determines seed shape, and ensures grain filling. Achieving optimal hull size and morphology is beneficial for seed development. We characterized the split-hull (sph) mutant in rice, which exhibits hull splitting in the interlocking part between lemma and palea and/or the folded part of the lemma during the grain filling stage. Morphological and chemical analysis revealed that reduction in the width of the lemma and lignin content of the hull in the sph mutant might be the cause of hull splitting. Genetic analysis indicated that the mutant phenotype was controlled by a single recessive gene, sph (Os04g0447100), which encodes a type-2 13-lipoxygenase. SPH knockout and knockdown transgenic plants displayed the same split-hull phenotype as in the mutant. The sph mutant showed significantly higher linoleic and linolenic acid (substrates of lipoxygenase) contents in spikelets compared to the wild type. It is probably due to the genetic defect of SPH and subsequent decrease in lipoxygenase activity. In dehulling experiment, the sph mutant showed high dehulling efficiency even by a weak tearing force in a dehulling machine. Collectively, the results provide a basis for understanding of the functional role of lipoxygenase in structure and maintenance of hulls, and would facilitate breeding of easy-dehulling rice.
由降低的外稃宽度和低木质素含量引起的半壳表型受 SPH 编码的 2 型 13-脂氧合酶控制，并有助于提高脱壳效率。稻壳由两个类似苞片的结构组成，即外稃和内稃。壳是一种重要的器官，有助于保护种子免受环境压力，决定种子形状，并确保灌浆。实现最佳的壳大小和形态有利于种子发育。我们对水稻中的半壳（sph）突变体进行了特征描述，该突变体在灌浆阶段表现出外稃和内稃之间的联锁部分和/或外稃折叠部分的壳分裂。形态和化学分析表明，sph 突变体中外稃宽度减小和壳木质素含量降低可能是壳分裂的原因。遗传分析表明，突变表型由单个隐性基因 sph（Os04g0447100）控制，该基因编码 2 型 13-脂氧合酶。SPH 敲除和敲低转基因植物表现出与突变体相同的半壳表型。与野生型相比，sph 突变体小穗中的亚油酸和亚麻酸（脂氧合酶的底物）含量明显更高。这可能是由于 SPH 的遗传缺陷和随后脂氧合酶活性的降低。在脱壳实验中，即使在脱壳机中施加较弱的撕裂力，sph 突变体也表现出较高的脱壳效率。总之，这些结果为理解脂氧合酶在壳结构和维持中的功能作用提供了依据，并将有助于培育易脱壳的水稻。
