Abstract
AtCYP19-4 (also known as CYP5) was previously identified as interacting in vitro with GNOM, a member of a large family of ARF guanine nucleotide exchange factors that is required for proper polar localization of the auxin efflux carrier PIN1. The present study demonstrated that OsCYP19-4, a gene encoding a putative homologue of AtCYP19-4, was up-regulated by several stresses and showed over 10-fold up-regulation in response to cold. The study further demonstrated that the promoter of OsCYP19-4 was activated in response to cold stress. An OsCYP19-4-GFP fusion protein was targeted to the outside of the plasma membrane via the endoplasmic reticulum as determined using brefeldin A, a vesicle trafficking inhibitor. An in vitro assay with a synthetic substrate oligomer confirmed that OsCYP19-4 had peptidyl-prolyl cis-trans isomerase activity, as was previously reported for AtCYP19-4. Rice plants overexpressing OsCYP19-4 showed cold-resistance phenotypes with significantly increased tiller and spike numbers, and consequently enhanced grain weight, compared with wild-type plants. Based on these results, the authors suggest that OsCYP19-4 is required for developmental acclimation to environmental stresses, especially cold. Furthermore, the results point to the potential of manipulating OsCYP19-4 expression to enhance cold tolerance or to increase biomass.
Highlights
Abiotic stresses have adverse effects on plant growth and development, and cold stress in particular significantly constrains the spatial distribution of plants and limits agricultural productivity (Thomashow, 1999)
The O. sativa ssp. japonica gene OsCYP19-4 (LOC_06g49470) encodes a protein of 208 amino acids containing a predicted endoplasmic reticulum (ER) signal peptide sequence at the N-terminus and a single peptidyl-prolyl cis-trans isomerase (PPIase) domain; it was classified as a putative homologue of AtCYP5 (AtCYP19-4) in a previous study (Ahn et al, 2010)
Putative monocot CYP19-4 homologues were identified by BLASTP searches with rice OsCYP19-4 as the query, and the proteins were aligned using ClustalW2 and visualized by using the GeneDoc program (Nicolas et al, 1997), revealing CYP20-1 cyclophilins to be similar to CYP19-4 proteins among higher plants (Jackson and Soll, 1999)
Summary
Abiotic stresses have adverse effects on plant growth and development, and cold stress in particular significantly constrains the spatial distribution of plants and limits agricultural productivity (Thomashow, 1999). Plants differ in their tolerance to chilling and freezing temperatures. Conventional breeding strategies to improve cold stress tolerance in various crop plants have not been successful owing to the complexity of stress tolerance traits, low genetic variation of yield components The transformation of a single gene appears to have a limited effect on crop freezing tolerance (Thomashow, 2001)
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