上海交大在PLOS子刊首次揭示基因DWT1调控水稻中的顶端优势现象


水稻的生长形态如株型、穗型、种子粒型等都对水稻产量具有重要影响。水稻植株由主茎和多个分蘖构成，主茎和分蘖之间的穗整齐度是影响水稻产量的另一重要因素。不同于野生稻，现代栽培水稻在人类驯化过程中形成了穗整齐生长的特征，株内主穗和各分蘖穗在成熟时期高度较为一致，穗大小也更为接近。这一特征的形成有利于获得更高的产量，但控制栽培稻穗整齐度的机制之前未见报道。

梁婉琪课题组通过对水稻突变体dwt1的研究，发现位于水稻一号染色体上的WOX类基因DWT1(DWARF TILLER1)在突变后会导致水稻分蘖节间不同程度缩短，从而引起分蘖明显矮化、穗变小，而主茎高度无显著变化且穗变大，类似于顶端优势加强的表型。

进一步研究发现DWT1在穗的枝梗原基中表达，通过一种非细胞自主的方式影响到穗下茎节节间的细胞分裂和伸长。DWT1可能通过影响一个未知的信号分子在穗部的合成或运输,调节穗下茎节中细胞分裂素的稳态以及茎节对赤霉素的响应能力，从而促进茎节伸长的这一重要发育过程。

DWT1在分蘖穗中的表达水平显著高于主茎中的表达水平，这一表达差异是造成主茎和分蘖高度差异的重要原因。

该研究不仅首次报道了水稻中的顶端优势现象，而且从分子水平上揭示了控制这一现象的一个关键基因DWT1的作用机理。该研究为进一步理解水稻植株形态的建成提供了新的认识，为阐明水稻整齐生长的分子机制找到了重要突破口。

原文摘要：

DWARF TILLER1, a WUSCHEL-Related Homeobox Transcription Factor, Is Required for Tiller Growth in Rice

Wenfei Wang, Gang Li, Jun Zhao, Huangwei Chu, Wenhui Lin, DABIng Zhang, Zhiyong Wang, Wanqi Liang

Unlike many wild grasses, domesticated rice cultivars have uniform culm height and panicle size among tillers and the main shoot, which is an important trait for grain yield. However, the genetic basis of this trait remains unknown. Here, we report that DWARF TILLER1 (DWT1) controls the developmental uniformity of the main shoot and tillers in rice (Oryza sativa). Mostdwt1 mutant plants develop main shoots with normal height and larger panicles, but dwarf tillers bearing smaller panicles compared with those of the wild type. In addition, dwt1 tillers have shorter internodes with fewer and un-elongated cells compared with the wild type, indicating that DWT1 affects cell division and cell elongation. Map-based cloning revealed that DWT1encodes a WUSCHEL-related homeobox (WOX) transcription factor homologous to theArabidopsis WOX8 and WOX9. The DWT1 gene is highly expressed in young panicles, but undetectable in the internodes, suggesting that DWT1 expression is spatially or temporally separated from its effect on the internode growth. Transcriptomic analysis revealed altered expression of genes involved in cell division and cell elongation, cytokinin/gibberellin homeostasis and signaling in dwt1 shorter internodes. Moreover, the non-elongating internodes of dwt1 are insensitive to exogenous gibberellin (GA) treatment, and some of the slender rice1(slr1) dwt1 double mutant exhibits defective internodes similar to the dwt1 single mutant, suggesting that the DWT1 activity in the internode elongation is directly or indirectly associated with GA signaling. This study reveals a genetic pathway synchronizing the development of tillers and the main shoot, and a new function of WOX genes in balancing branch growth in rice.

标签: 基因DWT1 水稻顶端优势现象 同源异型框基因 水稻穗整齐生长中

作者：上海交大

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