Table 1.

Overview of genes and their functions, and related mutants with altered root architecture in response to low P

Species	Gene name	Gene function during P starvation	Related phenotype grown in low P	References
Primary root
Arabidopsis	LPI1, LPI2	Pi starvation signalling	Longer primary root	Sánchez-Calderón et al. (2006)
Arabidopsis	PDR2	Pi starvation signalling	Shorter primary root	Ticconi et al. (2004)
Arabidopsis	PLDζ1	Pi starvation signalling	Retarded primary root growth	Li et al. (2006)
Arabidopsis	PLDζ2	Phospholipases	Retarded primary root growth	Li et al. (2006)
Arabidopsis	over Pht1;5	Pi starvation signalling	Shorter primary root	Nagarajan et al. (2011)
Arabidopsis	PHR1	Transcription factor, Pi starvation signalling	Slight reduction in the root-to-shoot ratio	Rubio et al. (2001); Bustos et al. (2010)
Arabidopsis	LPR1, LPR2	Hormone-like signalling	Primary root growth maintained	Svistoonoff et al. (2007)
Arabidopsis	PLT1/PLT2	Auxin signalling, meristem maintenance	Shorter primary root in double mutant	Aida et al. (2004)
Arabidopsis	SIZ1	SUMO E3 ligase; auxin signalling	Cessation of primary root growth	Miura et al. (2005, 2011)
Arabidopsis	PSI	Auxin signalling	Impaired inhibition of primary root	B.L. Wang et al. (2010)
Arabidopsis	VTC1	Ascorbate signalling	Shorter primary root	Tyburski et al. (2012)
Arabidopsis	GIN2	Sugar signalling	Shorter primary root	Karthikeyan et al. (2007)
Arabidopsis	FRY1	Phytochrome, light signal	Decrease in primary root elongation growth	Chen and Xiong (2010); Hirsch et al. (2011)
Rice	over OsPHR2	Pi starvation signalling	Enhanced induction rate of primary root	Zhou et al. (2008b)
Rice	OsMYB2P-1	Pi starvation signalling	Longer primary root	Dai et al. (2012)
Rice	LTN1	Pi starvation signalling	Enhanced elongation of primary root	Hu et al. (2011)
Lateral roots
Arabidopsis	LPR1	Hormone-like signalling	Reduced lateral root development	López-Bucio et al. (2005)
Arabidopsis	LPI	Pi starvation signalling	Reduced lateral root number	Sánchez-Calderón et al. (2006)
Arabidopsis	ARF7	Auxin signalling	More lateral roots	Pérez-Torres et al. (2008)
Arabidopsis	ARF19	Auxin signalling	More lateral roots	Pérez-Torres et al. (2008)
Arabidopsis	FRY1	Phytochrome, light signal	Reduced lateral root initiation and elongation	Chen and Xiong (2010); Hirsch et al. (2011)
Arabidopsis	SIZ1	SUMO E3 ligase; auxin signalling	Promoted lateral root growth	Miura et al. (2005, 2011)
Arabidopsis	PDR2	Pi starvation signalling	Numerous, short, highly branched lateral roots	Ticconi et al. (2004)
Arabidopsis	PLDζ1/PLDζ2	Phospholipases	Longer lateral roots	Li et al. (2006)
Arabidopsis	PLT1; 1PLT1; 4	Phosphate transport	Faster lateral root growth	Shin et al. (2004)
Arabidopsis	PNP	Methylerythritol-dependent biosynthesis	Numerous, short, highly branched lateral roots	Marchive et al. (2009)
Arabidopsis	GIN2	Sugar signalling	Reduction in the number of lateral roots	Karthikeyan et al. (2007)
Arabidopsis	WRKY 75RNAi	Transcription factor	Promoted formation of lateral roots	Devaiah et al. (2007a)
Rice	OsMYB2P-1	Pi starvation signalling	Longer adventitious roots	Dai et al. (2012)
Rice	over OsPHR2	Pi starvation signalling	Enhanced induction rate of adventitious roots	Zhou et al. (2008b)
Rice	LTN1	Pi starvation signalling	Enhanced elongation of adventitious roots	Hu et al. (2011)
Root hairs
Arabidopsis	LPI1, LPI2	Pi starvation signalling	Shorter root hair	Sánchez-Calderón et al. (2006)
Arabidopsis	bHLH32	Transcription factor	Increased root hair formation	Chen et al. (2007)
Arabidopsis	over Pht1;5	Pi starvation signalling	Increased root hair proliferation	Nagarajan et al. (2011)
Arabidopsis	SIZ1	SUMO E3 ligase; auxin signalling	Promoted root hair growth	Miura et al. (2005)
Arabidopsis	FBX2	Pi starvation signalling	Increased root hair formation	Chen et al. (2008)
Arabidopsis	IPK	Phytate synthesis	Constitutive production of root hairs	Stevenson-Paulik et al. (2005)
Arabidopsis	UBP14/PER1	Ubiquitin protease	Inhibition of root hair growth	Li et al. (2010)
Arabidopsis	HSP2	Ethylene signalling	Increased root hair formation	Lei et al. (2011b)
Arabidopsis	GA1,3	Gibberellic acid signalling	Shorter root hair	Jiang et al. (2007)
Arabidopsis	RSI4	bHLH transcription factor	Development of very short root hairs	Yi et al. (2010)
Arabidopsis	WRKY 75RNAi	Transcription factor	Constitutive production of root hairs	Devaiah et al. (2007a)
Arabidopsis	PHR1/PHL1	Pi starvation signalling	Inhibition in root hair growth	Bustos et al. (2010)
Arabidopsis	PHR1	Transcription factor, Pi starvation signalling	Increase in root hair length	Bustos et al. (2010)
Arabidopsis	PHL1	Pi starvation signalling	Sustains root hair length	Bustos et al. (2010)
White lupin	GPX-PDE1RNAi	Glycerophosphodiester phosphodiesterases	Reduction in root hair development	Cheng et al. (2011)
Cluster roots
White lupin	LaSAP1	Secreted acid phosphatase	Upregulated in P-deficient cluster roots	Wasaki et al. (1999)
White lupin	LaPT1	High-affinity Pi transporter	Upregulated in P-deficient cluster roots	Liu et al. (2001)
White lupin	LaMATE	Multidrug and toxin efflux	Upregulated in P-deficient cluster roots	Uhde-Stone et al. (2005)
White lupin	LaPEPC	Phosphoenolpyruvate	Upregulated in P-deficient cluster roots	Uhde-Stone et al. (2003a)
White lupin	LaGPX-PDE1	Glycerophosphodiester phosphodiesterases	Highly expressed in P-deficient cluster roots	Cheng et al. (2011)
White lupin	LaGPX-PDE2	Glycerophosphodiester phosphodiesterases	Highly expressed in P-deficient cluster roots	Cheng et al. (2011)
White lupin	CKX	Cytokinin signalling	Upregulated in P-deficient cluster roots	Vance et al. (2003)