Changes Of Proteome And Transcriptome Of Tobacco Leaf During Senescencing Process

Senescence which is the final stage of plant growth and development is highlyregulated and involved complex morphological and physiological changes at level ofcells, tissues, organs and whole plant etc. Tobacco is an important economic crop, andis used as model plant for botanical research as well. During period of tobacco fieldcultivation, the topping procedure changes normal senescence mode of tobacco leafinto special aging process which is closely related to quantities and qualities oftobacco production. Therefore, understanding mechanism of tobacco leaf senescencehas a great important significance on tobacco producing. Leaf senescence processinvolves in changing of morphology, physiology, signal transduction etc.，however thedetail mutual interactions and shifts of senescencing related gene expression in remainunknown. In this study, the field cultivating experiments with Tobaccocultivar“Yunyan87” were carried out in both Kunming and Lijiang Yongsheng ofYunnan province， and in Yongsheng, three different treatments of tobaccotransplanting time were applied and named T1,T2and T3respectively, and T2istransplanted in May3rdof2013according to long time local planting experiences,while T1(transplanting14days earlier than T2, and T3(14days later of T2), totalfour replicated treatments of “Yunyan87” were used for determination of agronomictraits, the SPAD value of in vivo chlorophyll, net photosynthetic rate (Pn),respirationrate (Rr) and other physiological changes of the middle part leaves of tobacco. The results show that with the development of leaf senescence, the length，width andthickness of leaves were gradually reduced, the contents of leaves chlorophyllsdecreased, The Pn decreased while Rr increased. According to those physiologicalchanges,5key middle leaves developing points which were prosperous stage (P), thephysiological mature stage (M),harvest stages(M1) delayed7days harvest(M2),delayed14days(M3), harvest were selected and collected for both proteomic andtranscriptomics analyzing. Results of proteome showed that protein expression relatedto leaf photosynthesis gradually decreased while protein related to respirationgradually increased; proteins related to translation process such as ribosome proteinand amino acid biosynthesis gradually weakened, however proteins related to proteinand amino acid degradation enhanced, and many stress tolerance proteins alsoup-regulated. However due to limited efficiency of proteomic analyzing, thetranscription factors, signal transduction, such as hormone signaling which playimportant roles on senescence regulation were undetectable on proteomic level, sofurther analysis of16DGEs with leaves samples of P, M, M1, M2stages from4different cultivated tobaccos in both Kunming and Lijiang area, the results showedthat the expression of senescence regulated transcription factors families,such asWRKY and NAC etc increased, the genes related to intracellular and cellulartransportation increased; the biosynthesis and signaling of growth promotionhormone such as IAA, GAs, reduced, while gene related to biosynthesis and signalingof senescence promoting endogenous hormones, such as ABA, JA, ethylene werereduced. Through the correlated analysis of proteome and DGEs, expressions of total25genes is consisted in both proteomic and trancripteomic levels, proving a moreconvinced gene collections of leaf senescence for their further function confirmation.In conclusion, genes related catabolism increase while anabolism decreased, plantseems treat senescence as stress and substance transportation from senescence leavesare extensively increases, our result indicating the changes climax of senescencechanges is occurred at M to M1stage which is tobacco leaves harvesting time intobacco fields producing. The study will benefit not only on elucidating thesenescence mechanism of tobacco leaves but also for high yields and high quality tobacco producing.