图1. 光信号通过调控内源脱落酸(ABA)和赤霉素(GA)的生物合成及信号转导调控种子休眠与萌发
(A) 光信号通过调控ABA和GA通路调控种子萌发。PHYB能够介导红光促进PIF1发生泛素化降解, 从而促进种子萌发。PIF1能够通过直接激活DAG1和SOM的转录进而间接调控GA生物合成相关基因的表达, 或者直接诱导DELLA蛋白编码基因RGA和GAI的转录, 最终抑制种子萌发。同样地, PIF1也能通过调控ABA的生物合成和信号转导调控种子萌发。PIF1通过依赖于SOM的途径促进ABA生物合成, 进而抑制种子萌发; 抑或直接诱导ABI3和ABI5的转录进而促进ABA信号转导, 抑制种子萌发。除PIF1之外, PHYB还能调控RVE1的转录间接促进GA的生物合成, 最终促进种子萌发。SPT和CSN蛋白复合体通过依赖于ABI5途径调控种子萌发。SPT通过抑制ABI5的转录抑制ABA信号转导, 促进种子萌发。CSN1通过促进RGL2的泛素化降解进而抑制ABI5的蛋白稳定性, 最终促进种子萌发; 而CSN5a能够直接抑制ABI5蛋白的积累进而促进种子萌发。JAZ3通过抑制ABI5对ABA响应基因EM1的转录激活功能进而促进种子萌发。(B) 光信号通过调控ABA和GA通路调控种子休眠。PHYB能够介导红光抑制RVE1转录, 进而促进下游GA3ox2的转录, 最终抑制种子休眠。在不同生态型拟南芥背景下, SPT调控种子休眠的功能不同。其中, 在Col背景下, SPT通过促进RGL3和ABI5的转录进而促进种子休眠(绿色标识线); 在Ler背景下, SPT通过抑制RGA和ABI4的转录进而抑制种子休眠(红色标识线)。此外, PIF6也参与调控种子休眠。

Figure 1. Light signal regulates seed germination and dormancy via endogenous abscisic acid (ABA) and gibberellin (GA) biosynthesis pathway
(A) Light signal regulates seed germination via ABA and GA pathway. PHYB regulates seed germination through promoting the degradation of PIF1 protein. The accumulation of PIF1 in nucleus activates the transcription of DAG1 and SOM, which indirectly regulates the expression of GA biosynthesis gene or directly induces RGA and GAI (DELLA protein encoding genes) transcription and leads to repressing seed germination. Similarly, PIF1 stimulates ABA biosynthesis and ABA signaling pathway to suppress seed germination. PIF1 induces ABA biosynthesis via SOM-dependent pathway to repress seed germination; or it induces the transcription of ABI3 and ABI5 in order to stimulate ABA signaling. Expect for PIF1, PHYB also promotes seed germination via inhibiting RVE1 transcription which indirectly promote GA biosynthesis. SPT and CSN complex could regulate seed germination in an ABI5-dependent manner. SPT suppresses ABI5 transcript to destroy ABA pathway. CSN1 stimulates RGL2 degradation to inhibit ABI5 activity, while CSN5a directly decreases the accumulation of ABI5 in order to provoke seed germination. JAZ3 promotes seed germination by repressing the transcriptional activity of ABI5 which activates ABA-responsing gene EM1 expression. (B) Light signal controls seed dormancy via ABA and GA pathway. PHYB mediates red light to repress the transcription level of GA3ox2, inhibiting seed dormancy. SPT plays different roles in regulating seed dormancy under Col and Ler background of Arabidopsis. SPT promotes seed dormancy through activating the expression of RGL3 and ABI5 under Col background (green line), however, SPT suppresses seed dormancy via inhibiting RGA and ABI4 transcript under Ler background (red line). In addition, PIF6 is also involved in controlling seed dormancy.