白头翁汤正丁醇提取物对酸性条件下白念珠菌pH突变株黏附的影响

目的 基于pH信号通路探讨白头翁汤正丁醇提取物(butyl alcohol extract of Baitouweng Decoction,BAEB)对白念珠菌黏附的影响。方法 Spotassay检测酸性条件下pH突变株的活性;XTT法检测酸性条件下pH突变株黏附时的代谢活力;荧光显微镜观察酸性条件下pH突变株细胞黏附活力;正辛烷容纳法测定酸性条件下pH突变株疏水性;实时荧光定量PCR(qRT-PCR)检测酸性条件下pH突变株黏附相关基因的表达。结果 512μg/m L BAEB对共培养24、48 h的pH突变株的活性影响不大;phr2/phr2在酸性条件下代谢活性低,512μg/m L BAEB可明显抑制白念珠菌野生株(WT)、PHR2回补菌株、rim101/rim101、RIM101回补菌株的代谢活性,对phr2/phr2代谢活性影响不大;512μg/m L BAEB可明显抑制WT、PHR2回补菌株、rim101/rim101、RIM101回补菌株的细胞黏附活力,phr2/phr2加药前后细胞黏附活性无明显变化;512μg/mL BAEB对WT、phr2/phr2、PHR2回补、rim101/rim101及RIM101回补菌株的细胞表面疏水性影响不明显;q RT-PCR法检测512μg/m L BAEB对pH突变株在酸性条件下黏附相关基因作用不明显,但1 024μg/m L BAEB则对大多数黏附相关基因有明显抑制作用。结论 BAEB在酸性条件下能一定程度抑制白念珠菌的黏附。

Two RING-Finger Ubiquitin E3 Ligases Regulate the Degradation of SPX4, An Internal Phosphate Sensor, for Phosphate Homeostasis and Signaling in Rice

SPX-domain-containing proteins (SPXs) play an important role in inorganic phosphate (Pi) sensing,signaling,and transport in eukaryotes.In plants,SPXs are known to integrate cellular Pi status and negatively regulate the activity of Pi central regulators,the PHOSPATE STARVATION RESPONSE proteins (PHRs).The stability of SPXs,such as SPX4,is reduced under Pi-deficient conditions.However,the mechanisms by which SPXs are degraded remain unclear.In this study,using a yeast-twhybrid screen we iden.tified two RING-finger ubiquitin E3 ligases regulating SPX4 degradation,designated SDEL1 and SDEL2,which were post-transcriptionally induced by Pi starvation.We found that both SDELs were located in the nucleus and cytoplasm,had ubiquitin E3 ligase activity,and directly ubiquitinated the K^213 and K^299 lysine residues in SPX4 to regulate its stability.Furthermore,we found that PHR2,a Pi central regulator in rice,could compete with SDELs by interacting with SPX4 under Pi-sufficient conditions,which protected SPX4 from ubiquitination and degradation.Consistent with the biochemical function of SDEL1 and SDEL2,overexpression of SDEL1 or SDEL2 resulted in Pi overaccumulation and induced Pi-starvation signaling even under Pi-sufficient conditions.Conversely,their loss-of-function mutants displayed decreased Pi accumulation and reduced Pi-starvation signaling.Collectively,our study revealed that SDEL1 and SDEL2 facilitate the degradation of SPX4 to modulate PHR2 activity and regulate Pi homeostasis and Pi signaling in response to external Pi availability in rice.

Modulation of nitrate-induced phosphate response by the MYB transcription factor RLI1/HINGE1 in the nucleus

The coordinated utilization of nitrogen(N)and phosphorus(P)is vital for plants to maintain nutrient balance and achieve optimal growth.Previously,we revealed a mechanism by which nitrate induces genes for phosphate utilization;this mechanism depends on NRT1.1B-facilitated degradation of cytoplasmic SPX4,which in turn promotes cytoplasmic-nuclear shuttling of PHR2,the central transcription factor of phosphate signaling,and triggers the nitrate-induced phosphate response(NIPR)and N-P coordinated utilization in rice.In this study,we unveiled a fine-tuning mechanism of NIPR in the nucleus regulated by Highly Induced by Nitrate Gene 1(HINGE1,also known as RLI1),a MYB-transcription factor closely related to PHR2.RLI1/HINGE1,which is transcriptionally activated by PHR2 under nitrate induction,can directly activate the expression of phosphate starvation-induced genes.More importantly,RLI1/HINGE1 competes with PHR2 for binding to its repressor proteins in the nucleus(SPX proteins),and consequently releases PHR2 to further enhance phosphate response.Therefore,RLI1/HINGE1 amplifies the phosphate response in the nucleus downstream of the cytoplasmic SPX4-PHR2 cascade,thereby enabling fine-tuning of N-P balance when nitrate supply is sufficient.