## 2 Results
### Transcriptional Regulators and Sensory Histidine Kinases  
Figures 2-9 indicate that the abundance patterns of the 293 transcriptional regulators and sensory histidine kinases fall into eight major clusters (A to H). Some were more abundant in Pi proficiency than in Pi limitation (Figure 2; cluster A) or more abundant in Pi limitation than in Pi proficiency (Figure 3, cluster B) in both strains. Other regulators were more abundant in \(SC\) than in \(SL\) in both Pi conditions (Figure 4, cluster C) or mainly in Pi proficiency (Figure 5, cluster D) or mainly in Pi limitation (Figure 6, cluster E) when other regulators were more abundant in \(SL\) than in \(SC\) in both Pi conditions (Figure 7, cluster F) or mainly in Pi limitation (Figure 8, cluster G) or mainly in Pi proficiency (Figure 9, cluster H). Sub-cluster A1 includes 22 regulators rather more abundant in Pi proficiency than in Pi limitation in both strains. Some of these regulators were more abundant in _SL_ than in _SC_ in Pi proficiency, such as the HU DNA-binding protein SCO5556 [58] whose poor abundance in _SC_ is likely to have a global impact on gene expression. Other regulators were more abundant in _SC_ than in _SL_ in both Pi conditions, such as ScbR/SCO6265 which positively controls the expression of the \(\gamma\)-buttyrolactone synthase ScbA/SCO6256 [59; 60]. ScbR in interaction with ScbA is involved in a bi-stable switch governing antibiotic production [61; 62]. However, most regulators had a similar abundance in the two strains, such as TamR/SCO3133 whose expression is induced in condition of OxS [63], the heat-inducible repressor HrcA/SCO2555 that controls positively the transcription of the groES-groEL1 operon, and of the groEL2 gene [64; 65] and sco7639 that is located in divergence of the enolase encoding gene sco7638. The regulator SCO7639 and the enolase SCO7638 were clearly more abundant in Pi proficiency than in Pi limitation in _SL_ (Figure 2 of [9]) suggesting that SCO7639 positively regulates sco7638 expression in conditions of Pi proficiency. However, despite the similar abundance of SCO7639 in _SC_ and in _SL_, the enolase SCO7638 and SCO3096 were poorly abundant in _SC_ (Figure 2 of [9]). This suggested that the presence/absence of a molecule acting as an allosteric effector or that a post-translational modification impairs the regulatory function of SCO7639 in _SC_. The sub-clusters A2 and A3 both include 16 regulators that were similarly abundant in _SL_ and _SC_ in Pi proficiency at both time points but also abundant in _SL_ in Pi limitation at 60 h. Sub-cluster A2 includes:  
* The response regulator (RR) OsaB/SCO5749 of TCS OsaA (HK)/OsaB whose expression is induced in conditions of OsS in a sigma B-dependent manner [66]. An OsaB mutant cannot erect aerial hyphae and produces up to 5-fold more antibiotic than the wild-type strain [66]. This TCS, involved in osmoadaptation, thus plays a negative role in the regulation of antibiotic production suggesting that high OsS contributes to the triggering of antibiotic production. * The sensory histidine kinase (SHK) DraK/SCO3062 of the TCS DraK/DraR. DraR was shown to directly activate the transcription of pathway-specific activator actII-ORF4 and thus ACT biosynthesis [67] whereas it represses CPK and RED biosynthesis via the repression it exerts on the expression of KasO, the specific activator of the CPK pathway, but its effect on RED biosynthesis is independent of the pathway-specific activators RedD and RedZ [67]. * The regulator DmdR1/SCO4394 controls iron homeostasis via the repression it exerts on the expression of the _desABCDE/sco2782-85_ cluster that directs the biosynthesis of the siderophore, desferrioxamine. Such repression is relieved in conditions of iron deprivation. Our previous data indicated that DesABCE were more abundant in _SL_ than in _SC_, especially in Pi proficiency, whereas, unexpectedly, the siderophore biosynthetic enzyme DesD, was highly abundant in both Pi conditions in _SC_ (Figure S12B of [9]).