Zhang Liguang, Ma Fei, Duan Guangxing, Ju Yan, Yu Tingqiao, Zhang Quan
Key Laboratory of Ministry of Education for Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing 100871, China.
Plant Physiol. 2024 Dec 23;197(1). doi: 10.1093/plphys/kiae576.
While pollen dormancy has been proposed to play a necessary role in sexual reproduction, it remains poorly understood. Here, we used traditional pollen germination assays to characterize dormancy. Our results underscore variation in the degree of dormancy between individual pollen grains. In addition, we provide evidence that JINGUBANG (JGB), previously defined as a negative regulator of pollen germination in Arabidopsis (Arabidopsis thaliana), is responsible for the uneven degrees of pollen dormancy, as asynchronous pollen germination in vitro reflected varied expression levels of JGB. We identified 5 cis-acting elements, including 4 CArG-boxes and the previously uncharacterized element ERE7, as essential for the initiation and enhancement of JGB expression. A 10-bp sequence between CArG-box 3 and ERE7, likely the result of an inverse DNA loop formed between CArG-box 3 and CArG-box 4, was required for robust gene expression. In addition, the pollen-specific AtMIKC*-type MADS transcription factors AGAMOUS-LIKE 30 (AGL30), AGL65, AGL66, AGL94, and AGL104 activated JGB transcription. Notably, the transactivation levels differed among the obligate AtMIKC* heterodimers tested. Our results indicate that distinct AtMIKC* complexes formed in individual pollen grains direct pollen dormancy to uneven degrees, which is likely an adaptive trait that ensures broader pollen dispersal under adverse environmental conditions.
虽然花粉休眠被认为在有性生殖中起着必要作用，但其仍未得到充分理解。在这里，我们使用传统的花粉萌发试验来表征休眠。我们的结果强调了单个花粉粒之间休眠程度的差异。此外，我们提供证据表明，先前被定义为拟南芥花粉萌发负调控因子的“金箍棒”（JGB），是花粉休眠程度不均一的原因，因为体外花粉萌发的不同步反映了JGB的不同表达水平。我们鉴定出5个顺式作用元件，包括4个CArG框和先前未表征的元件ERE7，它们对JGB表达的起始和增强至关重要。CArG框3和ERE7之间的一个10碱基序列，可能是CArG框3和CArG框4之间形成反向DNA环的结果，是强劲基因表达所必需的。此外,花粉特异性的AtMIKC型MADS转录因子AGAMOUS-LIKE 30（AGL30）、AGL65、AGL66、AGL94和AGL104激活JGB转录。值得注意的是，在所测试的专性AtMIKC异源二聚体中，反式激活水平有所不同。我们的结果表明，单个花粉粒中形成的不同AtMIKC*复合物导致花粉休眠程度不均一，这可能是一种适应性特征，可确保在不利环境条件下更广泛的花粉传播。
