Relationship between MdMADS11 Gene Expression and Juvenility in Apple

Abstract

Fruit trees have a long juvenile period after germination before flowering and fruit set. In spite of its horticultural importance, the physiological and molecular mechanisms of juvenility in fruit tree development are unknown; therefore, the relationship between the expression of the AGAMOUS-LIKE6 (AGL6) homolog and juvenility was investigated in apple (Malus domestica Borkh.). The results of sequence alignment, the phylogenetic tree, and Southern blot analysis suggested that MdMADS11 is an AGL6 ortholog in apple. An increase in the abundance of the mRNA of MdMADS11, which promotes flowering, corresponded to changes in leaf area and serration with the transition from the juvenile to adult phase in apple seedlings. In contrast, the abundance of mRNA of MdJOINTLESS, which may suppress flowering, decreased with the phase transition. Expression analysis of adult apple trees suggested that MdMADS11 also plays a role in seasonal flower initiation and floral organ formation in the adult phase. The results provide new insight into the molecular mechanism of the phase transition between juvenile and adult fruit trees.

Characterization of FLOWERING LOCUS C Homologs in Apple as a Model for Fruit Trees

“…MdFLC1c, which was the longest of the MdFLC1 mRNA variants, and MdFLC3 contained MADS-, K-, I-, and C-domains with AtFLC. A phylogenetic tree of the amino acid sequence of MdFLC1c, MdFLC3, and FLC homologous proteins from other plants was prepared with other MADS-box proteins based on [ 27 ] ( Figure 2 ). FLC, SVP, SOC1, AP1, and SEP groups were formed, and MdFLC1c and MdFLC3 were included in the FLC group.…”

“…Seasonal changes in the expression of MdFLC were examined in the adult trees. Flowering induction occurs between late June and mid-July [ 27 ]. The expression levels of MdFLC1a , MdFLC1b , and MdFLC1c were high in early June and decreased in early July during the period of flowering induction ( Figure 3 a–c).…”

“…In the present study, the expression levels of MdFLC1a , MdFLC1b , and MdFLC1c decreased during the period of flowering induction in a seasonal expression pattern in the adult trees. In the annual growth cycle of apple, MdFT1 , which is a floral integrator, shows high expression, and the expression level of MdTFL , which is a floral repressor, decreases during the period of flowering induction [ 9 , 27 ]. Therefore, the expression of MdFLC1a , MdFLC1b , and particularly MdFLC1c , which is expected to translate functional proteins, is likely involved in suppression of flowering in the annual growth cycle of adult apple trees, as is MdTFL .…”

“…Because phase change is observable in individuals, seedlings can be used for expression analysis of phase transition [ 36 ]. Five sites in the seedlings used in this study show phase transition based on juvenile characteristics such as flower bud formation, leaf size, and leaf serration, and were used for MdFLC expression analysis [ 27 ]. Although expression of MdFLC1a was not detected, the expression levels of MdFLC1b and MdFLC1c were high in the juvenile phase and low in the transitional and adult phases.…”

Characterization of PcLEA14, a Group 5 Late Embryogenesis Abundant Protein Gene from Pear (Pyrus communis)

“…Total RNA was extracted from pear using the cetyltrimethylammonium bromide method according to Hatsuda et al [ 41 ] and from Arabidopsis using the RNeasy Plant Mini Kit (QIAGEN, Hilden, Germany). The removal of genomic DNA and reverse transcription were performed using the Quantiscript Reverse Transcription Kit (QIAGEN) and Rever Tra Ace qPCR RT Master Mix (TOYOBO, Osaka, Japan).…”