Transcriptome profiles of contrasting potato (Solanum tuberosum L.) genotypes under water stress. Transcriptome profiles of contrasting potato (Solanum tuberosum L.) genotypes under water stress

The potato is susceptible to water stress at all stages of development. We examined four clones of tetraploid potato, Cardinal, Desirée, Clone 37 FB and Mije, from the germplasm bank of the National Institute of Agricultural Research (INIA) in Chile. Water stress was applied by suspending irrigation at the beginning of tuberization. Stomatal conductance, tuber and plant fresh and dry weight was used to categorize water stress tolerance. Cardinal had high susceptibility to water stress. Desirée was less suscepetible than Cardinal and had some characteristics of tolerance. Mije had moderate and Clon 37 FB high tolerance. Differential gene expression in leaves from plants with and without water stress were examined using transcriptome sequencing. Water stress susceptible Cardinal had the fewest differentially expressed genes at 101, compared to Desirée at 1867, Clon 37 FB at 1179 and Mije at 1010. Water stress tolerance was associated with up-regulation of expression of transcription factor genes and genes involved in osmolyte and polyamine biosynthesis. Increased expression of genes encoding late embryogenesis abundant (LEA) and dehydrin proteins along with decreased expression of genes involved in nitrate assimilation and amino acid metabolism were found for clones showing water stress tolerance. The results also show that water deficit was associated with reduced biotic stress responses. Additionally, heat shock protein genes were differentially expressed in all clones except for highly susceptible Cardinal. Together the gene expression study demonstrates variation in the molecular pathways and biological processes in response to water stress contributing to tolerance and susceptibility. Overall design: Comparison of the transcriptomic profile in 4 potato genotypes to drought stress in leaf samples

马铃薯在整个发育阶段均易遭受水分胁迫影响。本研究选取智利国家农业研究院（National Institute of Agricultural Research, INIA）种质库中的4个四倍体马铃薯克隆系：Cardinal、Desirée、Clone 37 FB及Mije。于块茎形成初期暂停灌溉以施加水分胁迫，通过测定气孔导度、块茎与植株的鲜重及干重，对各克隆系的水分胁迫耐受性进行分级。其中，Cardinal对水分胁迫敏感性极高；Desirée的敏感性弱于Cardinal，且具备部分耐受特性；Mije耐受性中等，Clone 37 FB则具有较高的耐受性。本研究通过转录组测序（transcriptome sequencing）分析了受水分胁迫与未受水分胁迫植株的叶片差异基因表达（differential gene expression）情况：水分胁迫敏感型的Cardinal差异表达基因最少，仅101个；相较之下，Desirée为1867个，Clone 37 FB为1179个，Mije为1010个。研究发现，水分胁迫耐受性与转录因子（transcription factor）基因、渗透调节物质（osmolyte）及多胺（polyamine）生物合成相关基因的上调表达密切相关；在耐受型克隆系中，可观察到胚胎发育晚期丰富蛋白（late embryogenesis abundant, LEA）与脱水蛋白（dehydrin）编码基因的上调表达，以及硝酸盐同化与氨基酸代谢相关基因的下调表达。此外，研究结果还显示水分亏缺会导致生物胁迫响应减弱；除高度敏感的Cardinal外，所有克隆系的热休克蛋白（heat shock protein）基因均存在差异表达。本基因表达研究整体揭示了响应水分胁迫的分子通路与生物学过程的变异，该变异是造成耐受性与敏感性差异的核心基础。总体实验设计：对4个马铃薯基因型在干旱胁迫下的叶片样本转录组谱进行比较分析。