Background Pears (Pyrus L.) are one of the leading cultivated fruit trees in China following apples and oranges in planting area and fruit yield.

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1 Nnjing Agriculturl University Potssium enhnces the sugr ssimiltion in leves nd fruit y regulting the expression of key genes involved in sugr metolism of Asin pers Cixi Dong, Chngwei Shen, Yngchun Xu College of Resources nd Environmentl Science, Nnjing Agriculturl University (NJAU) Bckground Pers (Pyrus L.) re one of the leding cultivted fruit trees in Chin following pples nd ornges in plnting re nd fruit yield. Yield Others 31% Apple 30% Other 43% Are Grpe 6% Apple 24% Per 14% Ornge 19% Per Ornge Hunggun Grpe (P. retschneideri 4% 13% 16% Rehd.) per is minly cultivted in the North of Chin. 1

2 Bckground K 67.9% K 占 67.9% Fruit C 占 4.3% Mg 占 4.6% N 占 18.7% P 占 K level in fruit is highest P 4.5% K is known s the qulity element in fruit production, which cn significntly improve fruit qulity Soil K depletion is mjor issue due to leching nd removl through fruit hrvest, nnul pruning, lef scission, etc. N 18.7% Reserch ckground on Sugr metoolism In pers nd other Roscee plnts, soritol is the min sugr for trnsporttion from leves to fruit, while sucrose is the minor one. Apple: Soritol in pple phloem ccounts for out 60 70% of totl sugrs, up to 80% in some vrieties; the sucrose ccounts for only 10 24% (Loescher 1987; Ymki 1986); Per nd pech: Soritol in phloem trnsport ccounts for out 70 80% (Ndwodnik nd Lohus 2008), nd sucrose is ccumulted up to 10% 53% of totl sugr in mture fruit flesh (Moriguchi et l., 1992; Zhng et l. 2012). 2

3 S6PDH SOT SDH SUT AIV SUS SPS Shnggun et l., 2014 Li et l., 2012 The flow of photosynthetic products (solule sugrs) from the leves into the fruit cn e promoted to provide certin osmotic potentil nd ccumulte more solule sugrs in fruit y K supply (Teo et l. 2006). Little reserch hs een reported on the mechnism of how to improve fruit sugr ccumultion y K. Reserch ckground on potssium Potssium is n essentil mcronutrient Enhnces fertility Promotes stress tolernce Regultes enzyme ctivities Strengthens cell wlls Stimultes photosynthte trnsloction Mintins turgor nd reduces wilting Regultes stomtl conductnce, photosynthesis nd trnspirtion Mintins ionic lnce [K + ] in soil = ~0.1 1 mm [K + ] in plnt cell cytoplsm = ~100 mm Symptoms of potssium deficiency See Wng, M., Zheng, Q., Shen, Q. nd Guo, S. (2013). The criticl role of potssium in plnt stress response. Intl. J. Mol. Sci. 14: ; 3

4 Mterils nd Methods Field study 16 yer old Asin per (P. retschneideri Rehd. cv. Hunggun ) trees Plnted t 4 m 5 m (the root stock ws P. etulefoli) 4 Potssium Levels: 0 (Control), 150 (K150), 300 (K300), 450 (K450) kg h 1 2 growing sesons (2014 nd 2015) Outline 1. SPAD nd photosynthetic chrcteristics in leves 2. Yield nd qulity index 3. K concentrtion nd ccumultion in leves nd fruit 4. Concentrtion of solule sugrs in leves nd fruit 5. Expression levels of key genes involved in sugr metolism in leves 6. Expression levels of key genes involved in sugr metolism in fruit 7. Redundncy nlysis (RDA) 4

5 1. SPAD nd photosynthetic chrcteristics in leves Compred to the Control, the Pn nd SPAD of the K450 hd n verge of 8.44% nd 2.71% higher, respectively. 2. Yield nd qulity index Averge of single fruit weight (g) K0 K150 K300 K450 K0 K150 K300 K c c c 10 c 5 10/5 22/6 20/7 12/ /5 7/5 11/6 16/7 16/ Yield (t h -1 ) 5

6 Firmness (l.cm -2 ) c 2. Yield nd qulity index Solule sugrs (%) e Sugr/cid c c c c c K0 K150 K300 K450 c 0 d Solule solids (%) Titrtle cidity ( ) K concentrtion nd ccumultion in leves nd fruit Young fruit Mturity Enlrgement One month fter hrvest 6

7 3. K concentrtion nd ccumultion in leves nd fruit 4. Concentrtion of solule sugrs in leves nd fruit The soritol concentrtion in leves nd fruits ws significntly incresed y K tretments during the fruit development stges At the mturity stge the sucrose concentrtion in fruit (sink) incresed with K ppliction rtes, while the sucrose ccumultion in leves (source) ws reduced. 7

8 5. Expression levels of key genes involved in sugr metolism in leves The ccumultions of solule sugrs (fructose, soritol, glucose, nd sucrose) in leves were correlted with the up-regulted expression of genes AIV nd S6PDH during the erly stges. The expression of AIV1, SPS1, SUS, S6PDH, ndsdh3 involved in sugr metolism in the leves were up-regulted y incresing the K ppliction rtes. T1:Log2(K150/K0) T2: Log2(K300/K0) T3:Log2(K450/K0) 6. Expression levels of key genes involved in sugr metolism in fruit The express levels of SPS1, SUS, SUT, SDH1 nd SDH3 were up-regulted y K t the mturity stge, which inproved the lrge ccumultion of sugrs 8

9 7. Redundncy nlysis (RDA) of K concentrtion, sugr metolites nd the expression of key genes involved in sugr metolism. Lef Fruit RDA2 RDA2 RDA1 RDA1 Lef K concentrtion: SOT3, SDH1, SDH3, S6PDH Fruit K concentrtion: SDH1, SUS A model of the effects of K on the expression of key genes involved in sucrose nd soritol from young fruit stge to mturity INV, S6PDH, SDH3 in lef SUT, SPS, SDH in fruit 9

10 Conclusion (1) Incresing K ppliction rtes led to promote the effectiveness of ccumultion of glucose, fructose, soritol, nd sucrose in fruit. (2) The ccumultion of fruit solule sugrs were not only ffected y the source-sink strength ut lso regulted y the inner regulting mechnism etween soritol nd sucrose metolism mong the leves nd fruit. (3) K plys key role on promoting the ssimiltion of photosynthetic products in leves nd fruit, nd up-regulting the expression of the key genes involved in sugr metolism in leves nd fruit. Further reserch (1) Trnscriptome nlysis of differentilly expressed genes induced y low nd high potssium levels in lef nd fruit of per. It cn provide insights into the mechnistic regultion of some cndidte genes, which cn revel the moleculr mechnism for improving fruit qulity with supplementl K fertilizers. Shen et l., Frontiers in plnt science, 2017, online 10

11 Further reserch (2) K supply cn promote the vsculr development of petiole nd fruit stlk, enhnce the distriution of nutrients nd sugr from lef to fruit. A: Petiole B: Fruit stlk Low K High K Acknowlegement This reserch ws supported y the Specil Fund for Agro-scientific Reserch in the Pulic interest ( ) Chin Agriculture Reserch System (CARS-29-15) 11

12 Nnjing Agriculturl University Thnk you for your ttention 12