背景回顾：Paradormancy of fruit trees occurs in summer and autumn when signals from adjacent organs stimulate buds to develop slowly. 

提出问题：This stage has received less attention that the other stages of dormancy, and the underlying mechanism remains uncharacterized. 

研究现象：Early defoliation in late summer and early autumn is usually followed by out-of-season blooming in pear (Pyrus spp.), which substantially decreases the number of buds the following spring and negatively affects fruit production. This early bud flush is an example of paradormancy release. 

结果1-落叶与芽中生长素含量：Here, we determined that flower bud auxin content is stable after defoliation; however, polar distribution of the pear (Pyrus pyrifolia) PIN-FORMED auxin efflux carrier 1b (PpyPIN1b) implied that auxin tends to be exported from buds. 

结果2-转录组分析：Transcriptome analysis of floral buds after artificial defoliation revealed changes in auxin metabolism, transport, and signal transduction pathways. 

结果3-外源NAA处理：Exogenous application of a high concentration of the auxin analog 1-naphthaleneacetic acid (300 mg/L) suppressed PpyPIN1b expression and its protein accumulation in the cell membrane, likely leading to decreased auxin efflux from buds, which hindered flower bud sprouting. 

结果4-其他因素：Furthermore, carbohydrates and additional hormones also influenced out-of-season flowering. 

结论：Our results indicate that defoliation-induced auxin efflux from buds accelerates bud paradormancy release. This differs from release of apical-dominance-related lateral bud paradormancy after the apex is removed. Our findings and proposed model further elucidate the mechanism underlying paradormancy and will help researchers to develop methods for inhibiting early defoliation-induced out-of-season bud sprouting.

Proposed model of the physiological process of autumn flowering before (left) and after (right) defoliation.

果树的类休眠发生在夏季和秋季，来自邻近器官的信号导致芽发育缓慢。对于果树类休眠的研究相对较少，尤其是分子调控机制方面的认识较少。梨树中，夏末和初秋的早期落叶往往伴随着反季节开花，从而极大地降低了来年春天的花芽数量，对来年的果实产量起到负面影响。这种秋季萌芽就是类休眠解除的一个例子。本文中，作者发现落叶后花芽中的生长素含量较为稳定；但是，生长素极性转运蛋白PpyPIN1b的极性分布暗示着生长素可能是从芽中往外运。通过对人工落叶后花芽的转录组分析，作者发现生长素代谢、转运和信号转导均发生了显著的改变。外源施加高浓度的生长素类似物NAA会抑制PpyPIN1b基因的表达及其蛋白在细胞膜中的积累，从而降低了生长素从芽往外的转运，从而阻止了花芽萌发。此外，碳水化合物和其他激素也会影响反季节开花。作者的研究揭示了落叶诱导的花芽中生长素外流会加速芽类休眠的解除。这不同于通过去除顶端，解除顶端优势施加于侧芽的类休眠。本文的研究及提出的模型进一步阐释了类休眠的机理，有助于研究者们开发出抑制早期落叶诱导反季节开花的方法。

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