Overexpression of phosphatidylserine synthase IbPSS1 affords cellular Na+homeostasis and salt tolerance by activating plasma membrane Na^(+)/H^(+)antiport activity in sweet potato roots

Phosphatidylserine synthase(PSS)-mediated phosphatidylserine(PS)synthesis is crucial for plant development.However,little is known about the contribution of PSS to Na^(+)homeostasis regulation and salt tolerance in plants.Here,we cloned the IbPSS1 gene,which encodes an ortholog of Arabidopsis AtPSS1,from sweet potato(Ipomoea batatas(L.)Lam.).The transient expression of IbPSS1 in Nicotiana benthamiana leaves increased PS abundance.We then established an efficient Agrobacterium rhizogenes-mediated in vivo root transgenic system for sweet potato.Overexpression of IbPSS1 through this system markedly decreased cellular Na^(+)accumulation in salinized transgenic roots(TRs)compared with adventitious roots.The overexpression of IbPSS1 enhanced salt-induced Na^(+)/H^(+)antiport activity and increased plasma membrane(PM)Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the TRs.We confirmed the important role of IbPSS1 in improving salt tolerance in transgenic sweet potato lines obtained from an Agrobacterium tumefaciens-mediated transformation system.Similarly,compared with the wild-type(WT)plants,the transgenic lines presented decreased Na^(+)accumulation,enhanced Na^(+)exclusion,and increased PM Ca^(2+)-permeable channel sensitivity to NaCl and H2O2 in the roots.Exogenous application of lysophosphatidylserine triggered similar shifts in Na^(+)accumulation and Na^(+)and Ca^(2+)fluxes in the salinized roots of WT.Overall,this study provides an efficient and reliable transgenic method for functional genomic studies of sweet potato.Our results revealed that IbPSS1 contributes to the salt tolerance of sweet potato by enabling Na^(+)homeostasis and Na^(+)exclusion in the roots,and the latter process is possibly controlled by PS reinforcing Ca^(2+)signaling in the roots.

Inhibition of miR397 by STTM technology to increase sweetpotato resistance to SPVD

As a critical food crop,sweetpotato(Ipomoea batatas(L.)Lam.)is widely planted all over the world,but it is deeply affected by Sweetpotato Virus Disease(SPVD).The present study utilized short tandem target mimic(STTM)technology to effectively up-regulate the expression of laccase(Ib LACs)by successfully inhibiting the expression of mi R397.The upstream genes in the lignin synthesis pathway were widely up-regulated by feedback regulation,including phenylalanine ammonialyase(PAL),4-coumarate-Co Aligase(4 CL),hydroxycinnamoyl Co A:shikimatetransferase(HTC),caffeicacid O-methyltransferase(COMT),and cinnamyl alcohol dehydrogenase(CAD).Meanwhile,the activities of PAL and LAC increased significantly,finally leading to increased lignin content.Lignin deposition in the cell wall increased the physical defence ability of transgenic sweetpotato plants,reduced the accumulation of SPVD transmitted by Bemisia tabaci(Gennadius),and promoted healthy sweetpotato growth.The results provide new insights for disease resistance breeding and green production of sweetpotato.

Ipomoea batatas HKT1 transporter homolog mediates K^+ and Na^+ uptake in Saccharomyces cerevisiae

Soil salinity causes the negative effects on the growth and yield of crops. In this study, two sweet potato （Ipomoea batatas L.） cultivars, Xushu 28 （X-28） and Okinawa 100 （O-100）, were examined under 50 and 100 mmol L-1 NaCI stress. X-28 cultivar is relatively high salt tolerant than O-100 cultivar. Interestingly, real-time quantitative polymerase chain reaction （RT-qPCR） results indicated that sweet potato high-affinity K^＋ transporter 1 （IbHKT1） gene expression was highly induced by 50 and 100 mmol L-1 NaCI stress in the stems of X-28 cultivar than in those of O-100 cultivar, but only slightly induced by these stresses in the leaves and fibrous roots in both cultivars. To characterize the function of IbHKT1 transporter, we performed ion-flux analysis in tobacco transient system and yeast complementation. Tobacco transient assay showed that IbHKT1 could uptake sodium （Na^＋）. Yeast complementation assay showed that IbHKT1 could take up K^＋ in 50 mmol L^-1 K^＋ medium without the presence of NaCI. Moreover, Na^＋ uptake significantly increased in yeast overexpressing IbHKTI. These results showed that IbHKT1 transporter could have K^＋-Na^＋ symport function in yeast. Therefore, the modes of action of IbHKT1 in transgenic yeast could differ from the mode of action of the other HKT1 transporters in class I. Potentially, IbHKT1 could be used to improve the salt tolerance nature in sweet potato.

A single-nucleotide substitution in the leucinerich-repeat-only gene CsLRR1 confers powdery mildew resistance in cucumber

Dear Editor,A variant with single substitution in the LRR-only protein CsLRR1,which regulates cucumber resistance to powdery mildew through a salicylic-acid-mediated pathway,provides a major source of resistance for cucumber breeding.Cucumber powdery mildew(PM),mainly caused by the biotrophic pathogen Podosphaera xanthii(synonym Podosphaera fusca),poses a serious threat to cucumber crops globally,leading to substantial reductions in fruit yield and quality(Martinez-Cruz et al.,2017).