Functions of two Malus hupehensis (Pamp.) Rehd. YTPs (MhYTP1 and MhYTP2) in biotic- and abiotic-stress responses

- The promoter regions of MhYTP1 and MhYTP2 contain many stress-related cis-elements.
- MhYTP1 and MhYTP2 participate in MeJA and SA signaling and their overexpression makes apple plants more susceptible to Marssonina apple blotch.
- Although expression of MhYTP1 and MhYTP2 can be induced by water-logging treatment, transgenic plants are more resistant to the oxygen deficiency that follows.
- MhYTP1 and MhYTP2 participate in plant responses to low and high temperatures, drought, high salinity, and nutrient deficiencies.

RNA binding proteins play important roles in plant responses to biotic and abiotic stresses. The YT521-B homology (YTH) domain-containing RNA binding protein (YTP) was first found in Rattus norvegicus and is related to oxygen-deficient stress. The Malus YTP gene family has 15 members. Results from their functional analysis will help researchers improve stress tolerance and fruit quality in apple. We cloned two homologous YTP family members in M. hupehensis - MhYTP1 and MhYTP2 - and identified their promoter regions that contain many cis-elements related to biotic and abiotic stresses. Both MhYTP1 and MhYTP2 can be induced by various treatments, e.g., methyl jasmonate (MeJA), salicylic acid (SA), abscisic acid (ABA), water-logging, water deficits, and high salinity. When compared with the wild type (WT), transgenic plants of 'GL-3' ('Royal Gala') apple that over-express MhYTP1 or MhYTP2 are more sensitive to D. mali infection, heat stress, and high salinity, more resistant to water-logging, chilling, drought and nutrition deficient conditions. All of these findings indicate that MhYTP1 and MhYTP2 participate in various biotic- and abiotic-stress responses.