Transitions of gene expression induced by short‐term blue light

Abstract

Blue light modulates many processes in plants and plant cells. It influences global and long-term responses, such as seedling development and phototropism, and induces short-term adaptations like stomatal opening and chloroplast movement. Three genes were identified as important for the latter process, namely PHOT1, PHOT2 and CHUP1. The former two phototropin blue light receptors act in perception of the blue light signal. The protein CHUP1 is localised to the outer envelope membrane of chloroplasts and is involved in chloroplast movement. To explore whether short-term reactions required for chloroplast movement are under transcriptional control, we analysed the transcriptome in wild-type Arabidopsis thaliana, phot1, phot2 and chup1 with different blue light treatments for 5 or 30 min. Blue light-induced changes in transcription depended on illumination time and intensity. Illumination with 100 μmol·m(-2) · s(-1) blue light induced down-regulation of several genes and might point to cascades that could be important for sensing low levels of blue light. Analysis of the transcriptome of the mutants in response to the different light regimes suggests that the transcriptional response to blue light in the wild-type can be attributed to phot1 rather than phot2, suggesting that blue light-induced alteration of expression is a function of phot1. In contrast, the blue light response at the transcriptional level of chup1 plants was unique, and confirmed the higher light sensitivity of this mutant.

Fine tuning chloroplast movements through physical interactions between phototropins

“…All mutants used in this study were T-DNA-containing SALK lines in the Col-0 background that have been described before: phot1 (At3g45780), SALK_088841 (Lehmann et al , 2011); phot2 (At5g58140), npl1-1 (Jarillo et al , 2001); rcn1-6 (At1g25490), SALK_059903 (Blakeslee et al , 2007); pp2a-b' γ (At4g15415), SALK_039172 (Trotta et al , 2011); pp2a-b'ζ1-1 (At3g21650), SALK_107944C (Rasool et al , 2014); and pp2a-2 (At1g10430), SALK_150673 (Wen et al , 2012). The rcn1-6 allele was selected instead of the rcn1-1 allele used by Tseng and Briggs (2010) because of its genetic background.…”

Systemic and Local Responses to Repeated HL Stress-Induced Retrograde Signaling in Arabidopsis

“…Interestingly, for both UVA and blue light the lack of systemic response is in despite of an observed strong physiological photobleaching response in the treated tissue (data not shown). This indicates the presence of separate retrograde signaling systems which activate HL SAA independent from those that govern blue light responses and photodamage acclimation responses (Franklin and Whitelam, 2004; Suetsugu and Wada, 2007; Takahashi et al, 2010; Lehmann et al, 2011). This is further supported by the observation that the white LEDs do not produce any UV spectra yet exhibit the highest induction of HL SAA and that HL SAA induction occurs at intensities as low as 250 μmol photons m −2 s −1 .…”

ROS-talk – how the apoplast, the chloroplast, and the nucleus get the message through

“…During the last 15 years the laws of organellar movement have started to be revealed, but the consequences of dynamic physical proximity and contact between the organelles are unknown (Suetsugu et al, 2010; Sakai and Haga, 2012). Recent studies demonstrate impairment of stress reactions in the Arabidopsis mutants which are unable to move chloroplasts in response to light stimuli or to dock them to the plasma membrane (Schmidt von Braun and Schleiff, 2008; Goh et al, 2009; Oliver et al, 2009; Lehmann et al, 2011). …”