Lateral root emergence in Arabidopsis is dependent on transcription factor LBD29 regulation of auxin influx carrier LAX3
Lateral root emergence in Arabidopsis is dependent on transcription factor LBD29 regulation of auxin influx carrier LAX3
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DOI：
10.1242/dev.136283
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发表时间：
2016-09-15
期刊：
影响因子：
4.6
通讯作者：
Bennett, Malcolm J.
中科院分区：
文献类型：
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作者：
Porco, Silvana;Larrieu, Antoine;Bennett, Malcolm J.
侧根原基（LRP）起源于位于亲本根组织深处的中柱鞘干细胞。 LRP 通过诱导生长素依赖性细胞分离和相邻细胞的水力变化而通过覆盖的根组织出现。生长素诱导型生长素流入载体 LAX3 在将信号集中到 LRP 上的细胞中发挥着关键作用。将 LAX3 表达限制在覆盖新 LRP 的两个相邻细胞文件中对于确保生长素调节的细胞分离仅沿着其共享壁发生至关重要。多尺度模型预测，这种高度集中的表达模式需要生长素依次诱导生长素流出和流入载体 PIN3 和 LAX3。与模型预测一致，我们报告生长素诱导的 LAX3 表达受生长素响应因子 7 (ARF7) 间接调节。酵母单杂交筛选显示，LAX3 启动子与转录因子 LBD29 结合，而 LBD29 是 ARF7 调节的直接目标。破坏生长素诱导的 LBD29 表达或表达 LBD29-SRDX 转录抑制子会复制 lax3 突变体的表型，导致侧根出现延迟。我们得出的结论是，生长素连续诱导 LBD29 和 LAX3 是协调细胞分离和器官出现所必需的。
Lateral root primordia (LRP) originate from pericycle stem cells located deep within parental root tissues. LRP emerge through overlying root tissues by inducing auxin-dependent cell separation and hydraulic changes in adjacent cells. The auxin-inducible auxin influx carrier LAX3 plays a key role concentrating this signal in cells overlying LRP. Delimiting LAX3 expression to two adjacent cell files overlying new LRP is crucial to ensure that auxin-regulated cell separation occurs solely along their shared walls. Multiscale modeling has predicted that this highly focused pattern of expression requires auxin to sequentially induce auxin efflux and influx carriers PIN3 and LAX3, respectively. Consistent with model predictions, we report that auxin-inducible LAX3 expression is regulated indirectly by AUXIN RESPONSE FACTOR 7 (ARF7). Yeast one-hybrid screens revealed that the LAX3 promoter is bound by the transcription factor LBD29, which is a direct target for regulation by ARF7. Disrupting auxin-inducible LBD29 expression or expressing an LBD29-SRDX transcriptional repressor phenocopied the lax3 mutant, resulting in delayed lateral root emergence. We conclude that sequential LBD29 and LAX3 induction by auxin is required to coordinate cell separation and organ emergence.