Effects Of SSR2,Its Expression And Potassium Supply On Glycoside Alkaloids In Potato(Solanum Tuberosum L.)

The SSR2 gene is a key,rate-limiting enzyme for potato glucoside alkaloid synthesis,and potassium deficiency is thought to be one of the factors that induce elevated alkaloid levels in many plants.To further reveal the relationship between SSR2 differences,expression and SGAs,and to analyze the effect of potassium on potato SGAs content,and to provide a basis for exploring feasible improved breeding pathways for potato SGAs and cultivation measures for regulating potato SGAs content,the present study used potassium starvation-varying potassium recovery concentrations(0,10,20 mmol/L)to determine the SGAs content,SSR2 expression and dry matter content of two test subjects(N5-48,Favorita),and to determine the SSR2 expression of three test subjects(N5-48,Favorita and Sichuan Taro No.5)under short-term potassium starvation treatment,and to clone the SSR2 gene sequence of four test subjects.The main findings and conclusions are as follows.1.There were very significant differences in the SGAs content between the N5-48 and Favorita seedlings,and between the SSR2 gene base sequences and amino acid sequences of the encoded proteins;however,differences in SSR2 structure may not be the main factor affecting the SGAs content between the two materials.2.The relative expression of SSR2 was found to be very significantly different between materials;in the potassium-deficiency-recovery treatment,SSR2 expression and SGAs were found to be similar in response to potassium concentration;correlation analysis also showed a very significant positive correlation between SGAs and SSR2 expression in both test materials.Thus SSR2 gene expression plays a decisive role in SGAs content.3.The SSR2 gene is highly conserved across species and the SGAs synthesis pathway may be indispensable for pest resistance and even normal growth and development of potato plants.Therefore,the idea of selecting commercial varieties of potato with low SGAs by silencing/knocking out SSR2 may not be realistic;and the most ideal breeding scheme for low SGAs may be to maintain the activity level of SSR2 in the stems and leaves of potato plants and to reduce and silence its expression in tubers.4.Different potassium recovery concentrations after potassium starvation had a significant combined effect on SGAs content;the overall expression was that low potassium conditions led to a sustained increase in SGAs,but the effects of persistent potassium deficiency on growth and metabolic activity could limit the level of SGAs.Potassium concentrations may not directly regulate SSR2 expression.5.Adequate potassium supplies should be maintained continuously in production to reduce SGAs in potato tubers,and appropriate potassium supplementation is required later in growth(tuber formation-expansion),including through foliar follow-up;this is also consistent with the technical requirements for fertilization in high-yielding potato cultivation.