Transcriptional memory and response to adverse temperatures in plants / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Temperature is one of the major environmental signals controlling plant development, geographical distribution, and seasonal behavior. Plants perceive adverse temperatures, such as high, low, and freezing temperatures, as stressful signals that can cause physiological defects and even death. As sessile organisms, plants have evolved sophisticated mechanisms to adapt to recurring stressful environments through changing gene expression or transcriptional reprogramming. Transcriptional memory refers to the ability of primed plants to remember previously experienced stress and acquire enhanced tolerance to similar or different stresses. Epigenetic modifications mediate transcriptional memory and play a key role in adapting to adverse temperatures. Understanding the mechanisms of the formation, maintenance, and resetting of stress-induced transcriptional memory will not only enable us to understand why there is a trade-off between plant defense and growth, but also provide a theoretical basis for generating stress-tolerant crops optimized for future climate change. In this review, we summarize recent advances in dissecting the mechanisms of plant transcriptional memory in response to adverse temperatures, based mainly on studies of the model plant

Adaptive thermogenesis of the brown adipose tissue in tree shrews (Tupaia belangeri) during cold acclimation / 中国实验动物学报

Objective To investigate the effect of ambient temperature on body mass, thermogenic activity and un-coupling protein-1 ( UCP1) content of brown adipose tissue ( BAT) in tree shrews ( Tupaia belangeri) , and to provide the-oretical basis for establishing tree shrews model of obesity.Methods Forty healthy adult tree shrews with similar body mass were uesd in our experiment.The tree shrews were divided into five groups (n=8):control group (0 d), the ani-mals were maintained under 25 ±1℃ and 12L:12D ( light : dark, lights on 08:00) photoperiod; and the animals were maintained under 5 ±1℃and 12L:12D photoperiod for 7 d, 14 d, 21 d and 28 d groups, respectively.At the end of ex-periment, the changes of body mass, nonshivering thermogenesis (NST), BAT mass and uncoupling protein 1 (UCP1) con-tent were determined.Results Compared with the control group (0 d), the body mass, NST, BAT mass and UCP1 con-tent of the cold acclimation groups were improved significantly, the BAT color also obviously deepened, and after cold accli-mation for 28 d, the body mass, NST, BAT mass and UCP1 content were increased by 26.32%, 20.65, 53.85%and 43%, respectively.Apparently, the UCP1 content was significantly positively correlated with BAT mass and NST.Conclusions BAT proliferation may be induced and UCP1 expression upregulated by cold acclimation in Tupaia belangeri, therefore, en-hancing the thermogenic activity of brown adipose tissue to increase energy expenditure.We would speculate that BAT might be used as a target organ for treatment of obesity by energetic approach in the future.

Switching between Heat Shock Proteins and Cold Inducible Proteins under Temperature Fluctuation in Solanum tuberosum L. Cultivars in In Vivo Condition.

Cross-talking between heat shock proteins (HSPs) and cold inducible proteins (CIPs) subsequent to combinational mild heat (35°C) and cold (8°C) stress was investigated in vivo for four cultivars of Solanum tuberosum L. viz. Kufri Pukhraj (PO), Kufri Jyoti (GS), Kufri Ashoka (KF) and Kufri Chandramukhi (CM) in the order of their decreasing thermotolerance, to understand how this economic crop adapts to extreme temperature fluctuation. We showed a time-course differential genotypic expression pattern for HSPs at 35°C for 10h and CIPs at 8°C for 12h time-lapse. Remarkably, we noted the disappearance of a housekeeping protein (HKP) of about 19.8KD at 2h, 35°C in GS absent in CM, KF and PO; but strongly expressed as CIPs at 8°C for all the cultivars. Furthermore, heat-stress led to an outstanding transient induction of HSP95.9, HSP83.6, HSP78.7, HSP70.7, HSP66.0, HSP54.1, HSP48.6, HSP43, sHSP38.3, sHSP35.3, sHSP29, sHSP22.5, sHSP17.8 and sHSP9.5 in GS at 6h, while HKP58.7, HKP55.5 and HKP43.7 were stably overexpressed in CM, KF and PO. Temperature switching from 35°C to 8°C upregulated HKP43.4, HKP54.6, CIP14.1 and HKP19.9 for all the cultivars. The recovery process 24h subsequent to this archetype switching was governed by overexpression of small(s)HSPs of about 25.4KD-14.1KD, HKP58.7 and HKP43.5 for all cultivars. Results suggest crosstalk protection for this paradigm-shift in temperature is chiefly conferred by isoforms of constitutively expressed HKPs, CIP19.9 and CIP14.1 in S. tuberosum L. Explicitly, this differential proteome change within 22h signify HKPs may not participate in thermotolerance as HSPs, but participate in cold acclimation as CIPs, recovery as sHSPs and even switch-off during heat-stress in some cultivars as depicted in GS.

Cold resistance in plants: a mystery unresolved

Herbaceous temperate plants are capable of developing freezing tolerance when they are exposed to low nonfreezing temperatures. Acquired freezing tolerance involves extensive reprogramming of gene expression and metabolism. Recent full-genome transcript profiling studies, in combination with mutational and transgenic plant analyses, have provided a snapshot of the complex transcriptional network that operates under cold stress. The changes in expression of hundreds of genes in response to cold temperatures are followed by increases in the levels of hundreds of metabolites, some of which are known to have protective effects against the damaging effects of cold stress. Genetic analysis has revealed important roles for cellular metabolic signals, and for RNA splicing, export and secondary structure unwinding, in regulating cold-responsive gene expression and chilling and freezing tolerance. These results along with many of the others summarized here further our understanding of the basic mechanisms that plants have evolved to survive freezing temperatures. In addition, the findings have potential practical applications, as freezing temperatures are a major factor limiting the geographical locations suitable for growing crop and horticultural plants and periodically account for significant losses in plant productivity. Although, great progress has been made in the field but lacunae still remain since it appears that the cold resistance is more complex than perceived and involves more than one pathway.

Fatty acid compositions of brown adipose tissue and skeletal muscles in cold-acclimated rats and rats reared in cold for successive generations / 体力科学

Triglyceride (TG) -fatty acid (FA) and phospholipid (PL) -FA profiles of skeletal muscles and brown adipose tissue (BAT) were examined in cold-acclimated rats (5°C, 4) (CA) and rats reared in cold for 25 generations (25 G) .<BR>1. TG of skeletal muscles: Polyunsaturated FA (PU) and unsaturation index (UI) were higher in soleus than in red and white muscles of quadriceps. In white muscle of CA saturated FA (SA) decreased and PU increased. This was also the case in white muscle of 25 G. In soleus of 25 G MU and PU increased, and SA decreased.<BR>2. PL of skeletal muscles: Higher SA, PU and lower MU were found in PL as compared with TG. In red muscle of CA SA increased while PU decreased. No significant changes were observed in white muscle and in soleus. In red muscle of 25 G a similar but more marked changes were found accompanied by lowered arachidonic acid and UI, thus suggesting decreased unsaturation of membrane lipid.<BR>3. TG of BAT: In CA SA increased and MU decreased. In 25 G SA and PU decreased and MU increased.<BR>4. PL of BAT: In CA SA, PU arachidonic acid, AI and UI increased, suggesting in-creased unsaturation of membrane lipid. In 25 G AI and arachidonic acid increased, but UI and PU were not changed.<BR>These results indicate that cold acclimation would cause significant alterations of FA profiles in tissues which has been shown to be involved in heat production in cold. Their significance, however, should await further study.