Transcriptome-Based Identification and Expression Profiling of AP2/ERF Members in Caragana Intermedia and Functional Analysis of CiDREB3

Caragana. intermedia Kuang et H.C.Fu., a xerophytic deciduous shrub that widely distributed in arid and semi-arid desert areas of North-west China, is highly tolerant to cold, drought, salt-alkali and barren. In this study, the transcriptome C. intermedia under drought treatment was screened for the genes encoding the AP2/ERF family of transcription factors. As a result, 22 sequences with complete open reading frames (ORFs) were obtained. All sequences were divided into 13 groups, including the DREB A1 to A6, ERF B1 to B6, and RAV groups. The results of multiple sequence alignment (MSA) analysis, domain distribution analysis, conservative motif analysis and tertiary structure prediction showed that all the AP2/ERF transcription factors contained the AP2 domain. The AP2 domain contained the YRG and RAYD elements. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was employed to analyze the expression patterns of the 22 AP2/ERF transcription factors in C. intermedia. Most of the transcription factors exhibited tissue-specific expression. The expression of most transcription factors was induced to varying degrees by cold, heat, salt and mannitol stress. Furthermore, Heterologous expression of CiDREB3 in transgenic Arabidopsis L. Heynh decreased root length and fresh weight, decreased rosette leaf diameter and number of leaf, and improved drought tolerance during seedlings development. Taken together, the results of the present study help to better understand the functions of the AP2/ERF family of transcription factors in plant responses to multiple abiotic stresses and deeply insight the roles of CiDREB3 in Arabidopsis morphology and conferring abiotic stress tolerance.

ADAPTATION OF Caragana intermedia TO ENVIRONMENTAL CHANGES WHILE GROWING: PHOTOSYNTHESIS AND WATER POTENTIAL

Plant photosynthesis is one of the most important physiological processes for plant survival and growth. Studies on the photosynthesis characteristics of sand-fixing vegetation of different ages in alpine sandy land provide a scientific basis and theoretical support for vegetation restoration and forest management in the region. In this study, the photosynthesis and water potential of Caragana intermedia plantations 5-, 7-, 10-, 12-, 18- and 32-year-old were measured, and meteorological data was obtained simultaneously. Results showed that utilization efficiency of light energy first decreased and then increased as plants grew; while in the case of CO2, utilization efficiency first increased and then decreased. The highest correlation coefficient between photosynthetic rate (Pn) and physiological or ecological factors were stomatal conductance (Gs) and CO2, respectively. Water potential of C. intermedia decreased then increased on a daily basis; but in old-aged individuals was significantly lower than that of the young-aged, showing a negative correlation with photosynthetically active radiation (PAR). Plants water consumption and water absorption capacity increase to resist external environment, in a physiological adaptation response to the increment of light.

Tree fine roots productivity and turnover rates estimation in alpine sandy land

Sequential coring method was used to collect the data of fine roots from June to August in alpine sandy land. Turnover rates were calculated by maximum or mean biomass during the growing season in 2015 using Decision Matrix (DM) or Maximum-Minimum (MM) method. Results show that biomass in June is lower than that in July and August. Turnover rates of Artemisia desertorum are higher than that of Caragana intermedia and Caragana korshinskii. Turnover rates of mixed forest are higher than that of pure forest. Soil gravimetric water content is highly related to root biomass/ length in the depth of 40 - 60 cm for Caragana intermedia and Caragana korshinskii. But soil gravimetric water content and root biomass/ length have no obvious regularity in the depth of 40 ~ 60 cm for Artemisia desertorum. The minimum water requirement threshold of around 0.02 can be acquired for Caragana intermedia and Caragana korshinskii in the arid region. In alpine sandy land, it is suitable to plant Artemisia desertorum compared to Caragana intermedia and Caragana korshinskii; mixed forest has more advantages compared to pure forest.

Analysis of Metabolite Accumulation Related to Pod Color Variation of Caragana intermedia

Caragana intermedia, a leguminous shrub widely distributed in cold and arid regions, is rich in secondary metabolites and natural active substances, with high nutritional and medical values. It is interesting that the pods of C. intermedia often show different colors among individual plants. In this study, 10-, 20- and 30-day-old red and green pods of C. intermedia were used to identify and characterize important metabolites associated with pod color. A total 557 metabolites, which could be classified into 21 groups, were detected in the pod extracts using liquid chromatography coupled with ESI-triple quadrupole-linear ion trap mass spectrometer (LC-ESI-MS/MS). Metabolomics analysis revealed significant differences in 15 groups of metabolites between red and green pods, including amino acids, nucleotide derivatives, flavonoids, and phytohormones. Metabolic pathway analysis showed that the shikimic acid and the phytohormone metabolic pathways were extraordinarily active in red pods, and the difference between red and green pods was obvious. Moreover, red pods showed remarkable flavonoids, cytokinins, and auxin accumulation, and the content of total flavonoids and proanthocyanidins in 30-day-old red pods was significantly higher than that in green pods. This metabolic profile contributes to valuable insights into the metabolic regulation mechanism in different color pods.