Down-regulation of SlCyp1 in the phloem reduces auxin response and photosynthetic rate in tomato (Solanum lycopersicum) plants

Abstract

The tomato dgt mutant, containing a single mutation in the Cyclophilin1 (SlCyp1) gene, is auxin insensitive and exhibits a pleotropic phenotype that includes lack of lateral roots, malformed xylem structure and reduced root-to-shoot ratio. Recently, we found that the SlCyp1 protein is phloem-mobile and traffic from shoot to root to induce lateral root formation. These processes are achieved through activation of auxin-mediated developmental programs. Inhibition of the trafficked SlCyp1 activity at the target site resulted in inhibition of the auxin response, supporting the hypothesis that this protein is indeed a mobile signal. Here, we show that partial silencing of SlCyp1 in the phloem only resulted in perturbed auxin response in the roots and reduced photosynthetic and transpiration rates. The presented data suggests that expression of SlCyp1 in the phloem is essential for proper auxin response at the whole plant level. We, therefore, propose that this protein acts as a long-distance signaling molecule acting as coordinator between roots and shoot activities.

Unraveling the Roles of Vascular Proteins Using Proteomics

“…The SlCyp1 protein is mobile in the phloem, and is transported from the shoot to the root to induce lateral root formation. Therefore, SlCyp1 integrates shoot photosynthesis with requirements for access to water and mineral nutrients in the roots [ 94 ]. Some plant pathogens, such as viruses and bacteria, can also spread systemically via the phloem throughout a host plant.…”

The interplay of phloem-mobile signals in plant development and stress response

“…The subsequent increase in HY5 TFs in the roots promotes NRT2.1 expression and potentiates NRT2.1-facilitated transport of nitrate from the soil [ 121 ]. Shoot-derived CYCLOPHILIN 1 (CYP1) in tomatoes integrates information about light intensity and photosynthetic status in the shoots with morphology and nutrient acquisition in the roots by influencing auxin response ( Figure 3 , pink) [ 122 , 123 ]. In addition, auxin directly controls root architecture as well.…”