Genome-wide comprehensive analysis of transcriptomes and small RNAs offers insights into the molecular mechanism of alkaline stress tolerance in a citrus rootstock.

Alkaline stress has serious-negative effects on citrus production. Ziyang xiangcheng (Citrus junos Sieb. ex Tanaka) (Cj) is a rootstock that is tolerant to alkaline stress and iron deficiency. Trifoliate orange (Poncirus trifoliata (L.) Raf.) (Pt), the most widely used rootstock in China, is sensitive to alkaline stress. To investigate the molecular mechanism underlying the tolerance of Cj to alkaline stress, next-generation sequencing was employed to profile the root transcriptomes and small RNAs of Cj and Pt seedlings that were cultured in nutrient solutions along a three pH gradient. This two-level regulation data set provides a system-level view of molecular events with a precise resolution. The data suggest that the auxin pathway may play a central role in the inhibitory effect of alkaline stress on root growth and that the regulation of auxin homeostasis under alkaline stress is important for the adaptation of citrus to alkaline stress. Moreover, the jasmonate (JA) pathway exhibits the opposite response to alkaline stress in Cj and Pt and may contribute to the differences in the alkaline stress tolerance and iron acquisition between Cj and Pt. The dataset provides a wealth of genomic resources and new clues to further study the mechanisms underlying alkaline stress resistance in Cj.