Molecular control of flowering regulation in mango
Mango is one of the most important crops of the tropical and subtropical world, with India being the largest producer. Flowering is an important aspect of plant biology and in mango it is one of the most crucial events for commercial success of the crop. Flowering behaviour of many preferred mango cultivars is irregular or shows alternate year flowering. A number of factors are responsible for induction of flowering, which includes horticultural, environmental, biochemical and genetic ones. Most of the genetic factors operate through an intricate network of genes. Over the past few years we performed characterization and expression studies of flowering pathway genes in this fruit. Gene homologues were identified, cloned, sequenced and their expressions were studied at different phenological stages in various plant tissues. The florigen or flowering factor FLOWERING LOCUS T (FT) gene identified in a model plant has a homologue that is also functional in mango and plays a central role in flowering regulation. It has at least three copies in the mango genome (MiFT1, MiFT2 and MiFT3). Structurally a close relative of FT, flowering repressor TERMINAL FLOWER LIKE 1 (TFL1), MiTFL1 and MiTFL1a are also involved in the regulation of flowering and especially in maintaining the vegetative phase. The FLOWERING LOCUS D (FD), which interacts with FT, was also identified as being involved in the regulation of flowering. Another important gene group are those regulated through the circadian rhythm. These are GIGENTIA (GI), FLAVIN BINDING KELCH REPEAT F BOX 1 (FKF1), CYCLIC DOF FACTOR 1 LIKE (CDF1) and CONSTANS (CO). GI-FKF1-CDF1-CO work as a module in this day-neutral crop. The presence of temperature sensitive elements in the promoter region of GI may be the key to the temperature-dependent flowering regulation in mango. Other genes involved are SUPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) and SHORT VEGETATIVE PHASE (SVP) as well as microRNAs. The microRNA 172 (miR172) is a positive regulator and microRNA 156 (miR156) is a negative regulator of flowering in mango. The interaction of above positive (MiCO1, MiCO2, MiFT1, MiFT2 and MiFT3, MiFD, MiGI2, MiSOC1 and MiCDF1) and suppressors (MiTFL1, MiTFL1a and MiSVP) leads to the expression of meristem identity genes APETALA 1 (MiAP1-1 and MiAP1-2) and LEAFY (MiLFY), which regulate the development of floral organs. An attempt has been made in this paper to give a comprehensive understanding of the regulation of flowering in mango in light of the current knowledge of the molecular biology of flowering.
Bal Krishna, Y., Vyavahare, S.N., Patil, S.I. and Sane, P.V. (2023). Molecular control of flowering regulation in mango. Acta Hortic. 1362, 97-106
TFL1, SVP, gene network, florigen factor, microRNA