Drought-induced proline is mainly synthesized in leaves and transported to roots in watermelon under water deficit

Proline accumulation has been shown to occur in plants in response to various environmental stresses.Although proline metabolismrelated genes have been functionally characterized,the inter-organ transport of proline in stressed plants remains unclear.In this study,free proline was detected with significant accumulations in the roots,stems,and leaves of watermelon drought-tolerant germplasm M08 and drought-susceptible line Y34 under drought stress.Expression profiling and enzyme activity measurements revealed that ClP5CS1 gene,rather than its paralog ClP5CS2,mainly contributes to the proline synthesis in leaves via the Glu pathway.Additionally,over-expression of the ClP5CS genes significantly enhanced the drought tolerance of transgenic Arabidopsis lines.Furthermore,we confirmed that proline is mainly synthesized in leaves and transported to roots in watermelon under drought stress.Transcriptome and expression analyses revealed that the genes involved in proline metabolism exhibited different expression levels.Specifically,ClP5CS1 was upregulated in leaves and roots,while ClP5CS2 was downregulated under drought stress.Also,415 and 362 differently expressed TFs were identified in roots and leaves,respectively,with the majority upregulated in the former.Ultimately,a model for proline metabolism was proposed.The findings of this study provided new insights into the biosynthesis,transport,and regulatory mechanism of drought-induced proline in plants.

Ectopic expression of VvFUS3,B3-domain transcription factor,in tomato influences seed development via affecting endoreduplication and hormones

FUSCA3(FUS3)is a member of B3-domain transcription factor family and master regulator of seed development.It has potential roles in hormone biosynthesis and signaling pathways and therefore plays diverse roles in plant life cycle,especially in seed germination,dormancy,embryo formation,seed and fruit development,and maturation.However,there is limited information about its functions in seed and fruit development of grapevine.In this study,we expressed VvFUS3 in tomato for its functional characterization.Overexpression of VvFUS3 in tomato led to a reduction in seed number and seed weight without affecting the fruit size.Histological analysis found that both cell expansion and cell division in transgenic seed and fruit pericarp have been affected.However,there were no obvious differences in pollen size,shape,and viability,suggesting that VvFUS3 affects seed development but not the pollen grains.Moreover,the expression of several genes with presumed roles in seed development and hormone signaling pathways was also influenced by VvFUS3.These results suggest that VvFUS3 is involved in hormonal signaling pathways that regulate seed number and size.In conclusion,our study provides novel preliminary information about the pivotal roles of VvFUS3 in seed and fruit development and these findings can potentially serve as a reference for molecular breeding of seedless grapes.