Abstract：
Transcription factors in coordination with phytohormones form an intricate regulatory network modulating vital cellular mechanisms like development, growth and senescence in plants. In this study, we have functionally characterized the transcription factor OsNAC121 by developing gene silencing and overexpressing transgenic rice plants, followed by detailed analyses of the plant architecture. Transgenic lines exhibited remodelling in crown root development, lateral root structure and density, tiller height and number, panicle and grain morphologies, underpinning the imbalanced auxin: cytokinin ratio due to perturbed auxin transportation. Application of cytokinin, auxin and abscisic acid increased OsNAC121 gene expression nearly 17-, 6- and 91-folds, respectively. qRT-PCR results showed differential expressions of auxin and cytokinin pathway genes, implying their altered levels. A 47-fold higher expression level of OsNAC121 during milky stage in untransformed rice, compared to 14-day old shoot tissue, suggests its crucial role in grain filling; as evidenced by a large number of undeveloped grains produced by the gene silenced lines. Crippled gravitropic response by the transgenic plants indicates their impaired auxin transport. Bioinformatics revealed that OsNAC121 interacts with co-repressor (TOPLESS) proteins and forms a part of the inhibitor complex OsIAA10, an essential core component of auxin signalling pathway. Therefore, OsNAC121 emerges as an important regulator of various aspects of plant architecture through modulation of crosstalk between auxin and cytokinin, altering their concentration gradient in the meristematic zones, and consequently modifying different plant organogenesis processes.
摘要：
转录因子与植物激素协调形成一个复杂的调节网络，调节重要的细胞机制，如发育，植物的生长和衰老。在这项研究中,我们通过开发基因沉默和过表达转基因水稻植物，对转录因子OsNAC121进行了功能表征，其次是对植物结构的详细分析。转基因品系在冠根发育中表现出重塑，侧根结构和密度，舵柄高度和数量，穗状花序和谷物形态，由于生长素运输受到干扰，支撑了生长素：细胞分裂素的比例不平衡。细胞分裂素的应用，生长素和脱落酸使OsNAC121基因表达增加近17-，6-和91-fold,分别。qRT-PCR结果显示生长素和细胞分裂素通路基因差异表达,暗示他们改变的水平。在未转化的水稻中，OsNAC121在乳白色阶段的表达水平提高了47倍，与14天大的枝条组织相比，表明其在籽粒灌浆中的关键作用；基因沉默的品系产生的大量未发育的谷物证明了这一点。转基因植物的重力响应减弱，表明其生长素转运受损。生物信息学显示，OsNAC121与共抑制蛋白（TOPLESS）相互作用，并形成抑制剂复合物OsIAA10的一部分，OsIAA10是生长素信号通路的重要核心成分。因此,OsNAC121通过调节生长素和细胞分裂素之间的串扰，成为植物结构各个方面的重要调节剂，改变它们在分生组织区域的浓度梯度，从而改变不同的植物器官发生过程。
