KNAP2, a class I KN1‐like gene is a negative marker of bud growth potential in apple trees (Malus domestica [L.] Borkh.)

• Published in: Journal of experimental botany 2002-11, Vol.53 (378), p.2143-2149
• Main Authors: Brunel, Nicole, Leduc, Nathalie, Poupard, Pascal, Simoneau, Philippe, Mauget, Jean‐Claude, Viémont, Jean‐Daniel
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Base Sequence; Biochemistry, Molecular Biology; Biological and medical sciences; Cell and Molecular Biology, Biochemistry and Molecular Physiology; Cellular Biology; Cloning, Molecular; Dormancy; Economic plant physiology; Environmental Sciences; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental - genetics; Gene Expression Regulation, Plant - genetics; Genes; Genetic Markers - genetics; Growth and development; Homeobox genes; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; In Situ Hybridization; Key words: In situ hybridization; KN1‐like genes; Leaf buds; Leaf primordia; Leaves; Life Sciences; Malus - cytology; Malus - genetics; Malus - growth & development; Malus domestica [L.] Borkh; Meristem - cytology; Meristem - genetics; Meristem - growth & development; Meristems; Molecular Sequence Data; morphogenesis; Morphogenesis, differentiation, rhizogenesis, tuberization. Senescence; Multigene Family; Plant growth. Development of the storage organs; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plant Shoots - cytology; Plant Shoots - genetics; Plant Shoots - growth & development; Plants; RNA; Seasons; Sequence Homology, Nucleic Acid; Vegetal Biology; Vegetative apparatus, growth and morphogenesis. Senescence; vegetative bud
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erf063

The determinism of bud bursting pattern along the 1‐year‐old shoot was studied at the molecular and morphological levels in the apple tree variety ‘Lodi’ which shows an acrotonic tendency. At the molecular level, the expression of KNAP2, which belongs to the class I KN1‐like gene family, was studied. Measurements were carried out during dormancy (October), breaking dormancy (January) and just before bud bursting (March). The results showed that KNAP2 is more highly expressed in buds that will remain at rest in the spring. Expression of KNAP2 was found in the meristem and in the marginal meristem of the two latest shaped primordia. In the January and March buds, this gene is also expressed in the procambial zone underneath the apical meristem. This study therefore suggests that KNAP2 may be considered as a negative marker of bud growth potential and that the growth inhibition in proximal buds could partially result from differential gene activity. At the morphological level, it was shown that no organogenetic activity took place between October and March as revealed by the constant number of leaf primordia in buds. Nevertheless, those buds likely to grow the following spring had a larger size and fewer hard scales than other buds. This suggests that genetic control may act together with other mechanisms, possibly physical (number of scales) or biochemical, to control bud inhibition.