**Zhilu Zhang \*, Zhonghua Liu, Haina Song, Minghui Chen and Shiping Cheng**

College of Chemistry and Environmental Engineering, Pingdingshan University, Pingdingshan 467000, China; hphy226@sohu.com (Z.L.); zhanglaoqi1234@sina.com (H.S.), zzl1111@tom.com (M.C.); chengship@163.com (S.C.)

**\*** Correspondence: zzl1111@pdsu.edu.cn

Received: 9 September 2019; Accepted: 21 September 2019; Published: 30 September 2019

**Abstract:** Leaf variegation has been demonstrated to have adaptive functions such as cold tolerance. *Pittosporum tobira* is an ornamental plant with natural leaf variegated cultivars grown in temperate regions. Herein, we investigated the role of leaf variegation in low temperature responses by comparing variegated "Variegatum" and non-variegated "Green Pittosporum" cultivars. We found that leaf variegation is associated with impaired chloroplast development in the yellow sector, reduced chlorophyll content, strong accumulation of carotenoids and high levels of ROS. However, the photosynthetic efficiency was not obviously impaired in the variegated leaves. Also, leaf variegation plays low temperature protective function since "Variegatum" displayed strong and efficient ROS-scavenging enzymatic systems to buffer cold (10 ◦C)-induced damages. Transcriptome analysis under cold conditions revealed 309 differentially expressed genes between both cultivars. Distinctly, the strong cold response observed in "Variegatum" was essentially attributed to the up-regulation of *HSP70*/*90* genes involved in cellular homeostasis; up-regulation of *POD* genes responsible for cell detoxification and up-regulation of *FAD2* genes and subsequent down-regulation of *GDSL* genes leading to high accumulation of polyunsaturated fatty acids for cell membrane fluidity. Overall, our results indicated that leaf variegation is associated with changes in physiological, biochemical and molecular components playing low temperature protective function in *P. tobira*.

**Keywords:** cold response; *Pittosporum tobira*; leaf variegation; linoleic acid; ROS scavenging enzyme; heat shock protein
