Yoon Jinmi, Cho Lae-Hyeon, Kim Song Lim, Choi Heebak, Koh Hee-Jong, An Gynheung
Crop Biotech Institute, Kyung Hee University, Yongin, 446-701, Korea; Department of Life Science, Pohang University of Science and Technology, Pohang, 790-784, Korea.
Plant J. 2014 Sep;79(5):717-28. doi: 10.1111/tpj.12581. Epub 2014 Jul 9.
Seed shattering is an important trait that influences grain yield. A major controlling quantitative trait locus in rice is qSH1. Although the degree of shattering is correlated with the level of expression of qSH1, some qSH1-defective cultivars display moderate shattering while others show a non-shattering phenotype. Os05 g38120 (SH5) on chromosome 5 is highly homologous to qSH1. Although we detected SH5 transcripts in various organs, this gene was highly expressed at the abscission zone (AZ) in the pedicels. When expression of this gene was suppressed in easy-shattering 'Kasalath', development of the AZ was reduced and thereby so was seed loss. By contrast, the extent of shattering, as well as AZ development, was greatly enhanced in moderate-shattering 'Dongjin' rice when SH5 was overexpressed. Likewise, overexpression of SH5 in the non-shattering 'Ilpum' led to an increase in seed shattering because lignin levels were decreased in the basal region of spikelets in the absence of development of an AZ. We also determined that two shattering-related genes, SHAT1 and Sh4, which are necessary for proper formation of an AZ, were induced by SH5. Based on these observations, we propose that SH5 modulates seed shattering by enhancing AZ development and inhibiting lignin biosynthesis.
种子脱落是影响谷物产量的一个重要性状。水稻中的一个主要控制数量性状基因座是qSH1。虽然脱落程度与qSH1的表达水平相关，但一些qSH1缺陷型品种表现出中度脱落，而其他品种则表现出不脱落的表型。位于第5号染色体上的Os05g38120（SH5）与qSH1高度同源。虽然我们在各个器官中检测到了SH5转录本，但该基因在花梗的脱落区（AZ）高度表达。当在易脱落的‘Kasalath’中抑制该基因的表达时，AZ的发育减少，从而种子损失也减少。相反，在中度脱落的‘Dongjin’水稻中过表达SH5时，脱落程度以及AZ的发育都大大增强。同样，在不脱落的‘Ilpum’中过表达SH5会导致种子脱落增加，因为在没有AZ发育的情况下，小穗基部区域的木质素水平降低。我们还确定，两个与脱落相关的基因SHAT1和Sh4，它们是AZ正常形成所必需的，受SH5诱导。基于这些观察结果，我们提出SH5通过增强AZ发育和抑制木质素生物合成来调节种子脱落。
