High impact information on PHB

• Role of PHABULOSA and PHAVOLUTA in determining radial patterning in shoots [1].
• We propose that the initial asymmetric leaf development is regulated primarily by mutual antagonism between KANADI and PHB-like genes, which is translated into polar YABBY expression [2].
• Simultaneous loss-of-function of PHABULOSA, PHAVOLUTA, and REVOLUTA abaxializes cotyledons, abolishes the formation of the primary apical meristem, and in severe cases, eliminates bilateral symmetry; these phenotypes implicate these three genes in radial patterning of both embryonic and postembryonic growth [3].
• In Arabidopsis, gain-of-function alleles of PHAVOLUTA and PHABULOSA, members of the class III HD-ZIP gene family, result in adaxialization of lateral organs [3].
• Thus, both WUS and PHB affect processes downstream of NZZ action during the transition from proximal--distal to adaxial--abaxial ovule development [4].

Biological context of PHB

• Low levels of methylation are detected in wt PHB DNA isolated from undifferentiated tissues [5].
• Here we show that the zinc-finger protein SERRATE acts in a microRNA (miRNA) gene-silencing pathway to regulate expression of the HD-Zip III gene PHABULOSA (PHB) while also limiting the competence of shoot tissue to respond to KNOX expression [6].

Regulatory relationships of PHB

• The alterations in polarity establishment are associated with expansion in the expression domain of the PHB-like genes and reduction in the expression of the previously described abaxial-promoting YABBY genes [7].

Other interactions of PHB

• We found that NZZ is required to restrict PHB expression to the distal chalaza, from where the inner integument initiates [4].
• PHB expression is not established in the distal chalaza of two mutants, aintegumenta (ant) and wus, which fail to form integuments [4].
• Furthermore, we examined the expression pattern of PHB, INO, and WUS in ovules of plants, which are affected in integument initiation and thus defective in the transition from proximal-distal to adaxial-abaxial development [4].

References