Suppression of Cs FAD3 in a JA-dependent manner,but not through the SA pathway,impairs drought stress tolerance in tea

The growth and yield of tea plants are seriously limited by drought stress.Fatty acid desaturases(FADs)contribute to the mediation of membrane fluidity in response to different stresses,although the role ofω-3 FAD(Omega-3fatty acid desaturase)-mediated damage induced by drought stress in tea plants is poorly understood.In this study,drought stress significantly promoted the synthesis of C18:3(linolenic acid)and the expression level of CsFAD3.Yeast experiments further demonstrated that CsFAD3 can convert C18:2 to C18:3,and that the 35S:GFP-CsFAD3fusion protein was localized in the endoplasmic reticulum of Nicotiana benthamiana cells.CsFAD3-silenced tea leaves exhibited poor drought tolerance,with a lower F_(v)/F_(m)and a higher malondialdehyde(MDA)content than the control plants.However,transgenic 35S:CsFAD3 Arabidopsis plants showed the opposite phenotypes.In addition,the jasmonic acid(JA)content and the expression levels of CsLOX2,CsLOX4,CsAOS,CsAOC3 and CsOPR2 were significantly reduced in CsFAD3-silenced leaves under drought stress.However,no substantial difference in the salicylic acid(SA)content was detected under normal or drought conditions.An analysis of Atcoi1(JA receptor)or Atnpr1(SA receptor)mutant Arabidopsis plants in 35S:CsFAD3 backgrounds further revealed that knockout of Atcoi1impaired the drought-tolerant phenotypes of CsFAD3 overexpression lines.Therefore,this study demonstrated that CsFAD3 plays a crucial role in drought tolerance by mediating JA pathways.

Characterization of CsWRKY29 and CsWRKY37 transcription factors and their functional roles in cold tolerance of tea plant

The WRKY gene family is most widely known as being the key plant transcription factor family involved in various stress responses and affecting plant growth and development.In this study,a total of 86 members of the CsWRKY genes were identified from the tea plant genome.Most of these genes contain several important Cis-regulatory elements in the promoter regions associated with multiple stress-responses.These genes were further classified into three groups,I,II,and III,each with 21,58,and 7 members,respectively.We showed evidence that tandem duplications,but not the whole genome duplication,are likely to drive the amplification of CsWRKY genes in tea plants.All the 86 CsWRKY genes showed differential expression patterns either in different tissues,or under exposure to diverse abiotic stresses such as drought,cold acclimation,and MeJA treatments.Additionally,the functional roles of two genes,CsWRKY29 and CsWRKY37,were examined under cold stress;and the silencing of these genes resulted in tea plant phenotypes susceptible to cold stress.Moreover,transgenic Arabidopsis lines overexpressing CsWRKY29 and CsWRKY37 genes showed higher survival rates and lower malondialdehyde levels under freezing treatment than the wild type plants.The core findings from this work provide valuable evolutionary pattern of WRKY gene family and underpinning the underlying regulatory roles of CsWRKY29 and CsWRKY37 from tea plants that conferred cold tolerance in transgenic Arabidopsis plants.

Efficient iron plaque formation on tea(Camellia sinensis) roots contributes to acidic stress tolerance

Tea plants grow in acidic soil, but to date, their intrinsic mechanisms of acidic stress tolerance have not been elucidated. Here, we assessed the tea plant response to growth on NHt4 nutrient media having different p H and iron levels. When grown in standard NHt4 nutrient solution(iron insufficient, 0.35 mg Là1 Fe2t), tea roots exhibited significantly lower nitrogen accumulation, plasma membrane Ht-ATPase activity, and protein levels; net Htefflux was lower at pH 4.0 and 5.0 than at pH 6.0. Addition of30 mg Là1 Fe2t(iron sufficient, mimicking normal soil Fe2tconcentrations) to the NHt4 nutrient solution led to more efficient iron plaque formation on roots and increased root plasma membrane Ht-ATPase levels and activities at p H 4.0 eland 5.0, compared to the p H 6.0 condition. Furthermore,plants grown at pH 4.0 and 5.0, with sufficient iron,exhibited significantly higher nitrogen accumulation than those grown at pH 6.0. Together, these results support the hypothesis that efficient iron plaque formation, on tea roots, is important for acidic stress tolerance. Furthermore,our findings establish that efficient iron plaque formation is linked to increased levels and activities of the tea root plasma membrane Ht-ATPase, under low pH conditions.