| Global climate change is leading to more extreme droughts and floods,which pose a serious threat to plants.Cinnamomum chago B.S Sun et H.L.Zhao is an evergreen broad-leaved tree of the genus Cinnamomum belongs to the family Lauraceae.At present,it is only distributed in a narrow area of Dali Prefecture,Yunnan Province,and its population is rare.C.chago is tall with thick canopy and fine wood,its seeds are edible.C.chago is a high-quality greening,economic and timber tree species.It has been listed as a secondary protected plant of the National Key Protected Wild Plants.Meanwhile,it has been listed in the list of Wild Plants with Extremely Small Population in Yunnan Province(2021),which needs effective protection.However,little is known about the biological characteristics of C.chago at present.In this study,the changes of photosynthetic characteristics,physiological and biochemical characteristics of C.chago seedlings under different Soil Relative Water Content(RSWC),namely control(CK,75%一 80%),slight water deficit(T1,55%～60%),moderate water deficit(T2,40%～45%),severe water deficit(T3,30%～35%)and excess water(T4,85%～90%)were studied to explore the physiological mechanism of C.chago to adapt to water stress.At the same time,transcriptome sequencing was used to analyze the gene differential expression of C.chago under water stress,exploring the genes involved in water stress and their metabolic pathways,and revealing the molecular mechanism of C.chago seedlings in response to water stress.The results will provide a scientific basis for the effective conservation,seedling cultivation and resource development and utilization of C.chago germplasm resources.The main results are as follows:1.The photosynthetic characteristics of C.chago seedlings under different water condition showed that water stress reduced the photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and water use efficiency(WUE).The diurnal variation of Pn showed a "single peak" mode in CK and T4 treatment,without obvious"midday depression of photosynthesis",but showed a downward trend with time in T1,T2 and T3 treatment.Under the same photosynthetic effective radiation(PPFD)or the same CO2 concentration,the Pn value of C.chago seedlings showed CK>T4>T1>T2>T3.Water stress decreased the maximum net photosynthetic rate(Pnmax),apparent quantum yield(a),dark respiration rate(Rd),rubisco maximum carboxylation rate(Vcmax),maximum electron transfer rate(Jmax)and photorespiration rate(Rp)of C.chago seedlings.In addition,maximum PSII quantum efficiency(Fv/Fm)decreased as a whole under water stress,while quantum yield of PSII(Yield)and electron transfer rate(ETR)increased slightly under T1 treatment,but decreased significantly under T3 and T4 treatment,and their change trend are consistent2.The results of physiological and biochemical characteristics of C.chago seedlings showed that water stress increased the contents of proline(Pro),soluble sugar(SS),malondialdehyde(MDA)and superoxide dismutase(SOD)of C.chago seedlings,indicating that C.chago seedlings responded to water stress by accumulating the contents of the above physiological indexes.Severe water deficit significantly reduced the carotenoid(Car)of C.chago seedlings.According to the analysis of stress resistance by membership function,it suggests that C.chago seedlings was of moderately resistance and the SRWC of 75%～80%was the most suitable for the growth of C.chago seedlings.3.Transcriptome sequencing analysis showed that 69343 Unigene with an average length of 1079.57bp were obtained,7693 significant expressed genes(DEGs)were identified.The functional enrichment analysis of these DEGs showed that the genes involved in plant hormone signal transduction,photosynthesis,starch and sucrose metabolism,flavonoid biosynthesis and phenylpropanoid biosynthesis were highly enriched under water stress,in which the expression of photosynthesis related genes were down-regulated and the expression of phenylpropanoid biosynthesis related genes were up-regulated.4.Weighted gene co-expression network analysis(WGCNA)of C.chago seedlings under water stress showed that a total of 4761 filtered genes were obtained from 15 samples of C.chago,and 13 trait related modules were constructed,of which 6 were significantly related.The functional enrichment analysis of these six modules showed that the genes involved in starch and sucrose metabolism,plant hormone signal transduction,phenylpropanoid biosynthesis,plant-pathogen interaction,metabolism of cofactors and vitamins pathway were significantly enriched under water stress.Combined with the results of DEGs enrichment showed that under water stress,C.chago seedlings mainly adapt to water stress by regulating the gene expression related to plant hormone signal transduction,photosynthesis,starch and sucrose metabolism,flavonoid biosynthesis and phenylpropanoid biosynthesis.In conclusion,C.chago seedlings responded to water stress mainly through the coordination of photosynthesis,physiological biochemistry and gene regulation.Under water stress,as a response of C.chago seedlings to water stress signals,related regulatory genes were activated,resulting in changes in gene expression of functional proteins,which resulted in corresponding changes in photosynthetic characteristics,physiological and biochemical parameters.Under water stress,the change of cell fluid concentration induced the expression of genes involved in osmotic regulation,promoted the accumulation of osmotic substances,and the osmotic regulation ability was enhanced.Meanwhile,the peroxide signal was enhanced,which promoted C.chago seedlings to alleviate the peroxide damage caused by water stress by increasing the activity of antioxidant enzymes. |
PDF Full Text Request