Blue‐light‐induced PIN3 polarization for root negative phototropic response in Arabidopsis

Abstract

SUMMARYRoot negative phototropism is an important response in plants. Although blue light is known to mediate this response, the cellular and molecular mechanisms underlying root negative phototropism remain unclear. Here, we report that the auxin efflux carrier PIN-FORMED (PIN) 3 is involved in asymmetric auxin distribution and root negative phototropism. Unilateral blue-light illumination polarized PIN3 to the outer lateral membrane of columella cells at the illuminated root side, and increased auxin activity at the illuminated side of roots, where auxin promotes growth and causes roots bending away from the light source. Furthermore, root negative phototropic response and blue-light-induced PIN3 polarization were modulated by a brefeldin A-sensitive, GNOM-dependent, trafficking pathway and by phot1-regulated PINOID (PID)/PRO-TEIN PHOSPHATASE 2A (PP2A) activity. Our results indicate that blue-light-induced PIN3 polarization is needed for asymmetric auxin distribution during root negative phototropic response.

Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation

“…Auxin efflux or influx carriers are involved in these changes in auxin 433 accumulation and distribution (Hong et al, 2014;Liu et al, 2015;Yan et al, 2013;434 Yuan et al, 2013;Yuan et al, 2014;Zhang et al, 2013;Zhang et al, 2014;Zhu et al, 435 2014). Moreover, PIN2 participates in alkaline stress-mediated root inhibition (Xu et 436 al., 2012).…”

Light Signaling, Root Development, and Plasticity

“…Downstream of directional light perception, polar auxin transport directs auxin away from the illuminated side. This auxin transport gradient requires rootward plasma membrane localization of the auxin efflux carrier PIN1 in the stele, lateral relocalization of PIN3 in the columella, and rootward relocalization of PIN2 in the epidermis (Wan et al, 2012;Zhang et al, 2013Zhang et al, , 2014. The relocalization of PIN2 and PIN3 is dependent upon the recycling and targeted degradation (vacuolar targeting) of these PIN carriers from one side of the membrane to the other (Wan et al, 2012;Zhang et al, 2013).…”

“…There are two PHOTs identified in Arabidopsis, phot1 and phot2, with similar function and structure. Besides their function in the shoot, phot1 is also expressed in the roots, regulating root bending (Wan et al, 2012;Zhang et al, 2013). In contrast to other photoreceptors, which are present in the nucleus or cytoplasm, PHOTs are located in the plasma membrane (Sakamoto and Briggs, 2002).…”

“…Light influences the direction of polar auxin transport by controlling the plasma membrane abundance of PIN proteins (Laxmi et al, 2008;Sassi et al, 2012;Wan et al, 2012;Zhang et al, 2013Zhang et al, , 2014). An interesting example of how light interacts with the gravitropic output is the U-turn that an inverted maize (Zea mays) seedling root makes when growing in a glass tube exposed to light (Burbach et al, 2012;Suzuki et al, 2016).…”

“…This auxin transport gradient requires rootward plasma membrane localization of the auxin efflux carrier PIN1 in the stele, lateral relocalization of PIN3 in the columella, and rootward relocalization of PIN2 in the epidermis (Wan et al, 2012;Zhang et al, 2013Zhang et al, , 2014. The relocalization of PIN2 and PIN3 is dependent upon the recycling and targeted degradation (vacuolar targeting) of these PIN carriers from one side of the membrane to the other (Wan et al, 2012;Zhang et al, 2013). The initial perception of gravitropism and phototropism is different, but the downstream signaling events of negative phototropism are very similar to those found in root gravitropism, involving comparable PIN protein and auxin transport dynamics (Friml et al, 2002;Abas et al, 2006;Baster et al, 2013).…”