Photoreceptor PhyB Involved in Arabidopsis Temperature Perception and Heat-Tolerance Formation

Abstract

The influence of temperature on plants is essential. However, our knowledge on the intricate regulation process underlying heat stress (HS) response in plants is limited. Recently, information about thermal sensors in vivo has begun to emerge. In this study, another primary environmental stimulus, light, was verified once again to work with temperature synergistically on plants, through the modulation of numerous biological processes. With the application of transcriptomic analysis, a substantial number of heat-responsive genes were detected involved in both light- and phytohormone-mediated pathways in Arabidopsis. During this process, phytoreceptor phyB acts as a molecular switch to turn on or turn off several other genes HS response, under different light conditions. Furthermore, a morphological study showed the afunction of phyB enhanced plants thermal tolerance, confirming the important role of this phytochrome in temperature perception and response in plants. This study adds data to the picture of light and temperature signaling cross-talk in plants, which is important for the exploration of complicated HS responses or light-mediated mechanisms. Furthermore, based on its influence on Arabidopsis thermal response in both morphological and physiological levels, phyB is a photoreceptor, as revealed before, as well as an essential thermal sensor in plants.

Keywords: Arabidopsis thaliana; heat stress response; interplay between abiotic stresses; photoreceptor-phyB; transcriptomic and morphological analysis.

Figure 1

GO enrichment analysis of differentially expressed genes to HS treatment. GOEAST analysis reveals that the heat stress (HS)-induced differentially expressed genes are enriched into several biological processes (see original map in Supplemental KEGGS and GOEASTs). A statistics summary of biological processes on Level 4 (the 4th rank of GOEAST-biological_process, see Supplementary GOEAST GENE LIST) is presented here. On this level, 18.39% and 11.87% of the HS-induced genes are involved in hormone stimulus and light stimulus response, respectively. (Genes involving more than one category are double-counted. Red frames highlight the three “responses”.)

Figure 2

Relative expression of auxin-metabolism related genes. For both qPCR and microarray analysis, plants grown at 23 °C were collected as control group, and plants grown at 37 °C were collected as HS group. ACTIN2 was used as an internal reference for both assays.

Figure 3

Transcriptomic response to HS, under different light conditions treatment (compared to control plants, ACTIN2 used as internal references). Plants grown at 23 °C are chosen as control. mRNA extraction and qPCR experiments are conducted as described in the method. HS + WL: Plants in this group are treated at 37 °C for 30 min, under white light. HS + RL: Treated at 37 °C for 30 min, under red light. HS + FRL: Treated at 37 °C for 30 min, under far-red light. HS + BL: Treated at 37 °C for 30 min, under blue light. WL, white light; RL, red light; FRL, far-red light; BL, blue light. The histogram (A) shows the expressions of genes in different light conditions; the table (B) demonstrated the similarity between BL and FRL groups (green frames), and the particularity of RL group (red frames). Blue shadow means the gene expression was repressed by HS. Red shadow means enhanced.

Figure 4

Survival analysis of different Arabidopsis genotypes under HS treatment. After treatment at 37 °C for three days, about 44% and 40% col-0 and phyA seedlings still survive (see (A,B)); However, the survival rate of phyB is more than 70% (see (C)).

Figure 5

Root development of three genotypes of Arabidopsis (control individuals were placed on the right, treated ones left), and statistical summary for phenotype analysis. After treatment at 37 °C for three days, the main roots lengths of all three genotypes were suppressed to a similar degree. Meanwhile, the lateral root development of col-0 and phyA seedlings are severely inhibited (see (A,B,D)). However, the lateral roots of phyB showed superior development (see (C,D)). Scale bars, 1 mm.