Arabidopsis BRANCHED1Acts as an Integrator of Branching Signals within Axillary Buds

We describe an Arabidopsis gene encoding a TCP transcription factor closely related to teosinte branched1 from maize, BRANCHED1, which represents a key point at which signals controlling branching are integrated within axillary buds

José Antonio Aguilar-Martínez; César Poza-Carrión; Pilar Cubas

2007

Scholarcy highlights

  • The vast diversity of plant architectures found in plants today depends largely on the control of branching
  • To identify the Arabidopsis genes closest to tb1, the complete Arabidopsis TCP gene family was analyzed. This family comprised 24 genes encoding predicted proteins with a TCP domain. Phylogenetic analysis of this domain revealed two subfamilies: class I, formed by 13 predicted proteins related to the PCF rice factors, and class II, formed by 11 predicted proteins related to the Antirrhinum CYC and CIN genes and to tb1
  • Class II could be further subdivided into two groups: the CIN group formed by eight members, some of which are involved in the control of leaf primordia growth, and the tb1/CYC group, on which we have focused
  • Leaves of the axillary buds grew faster and were larger than wild-type leaves. This effect was more dramatic in plants grown under short days, in which wild-type and mutant axillary meristems were initiated before flowering and bud development was prolonged for many weeks. These results indicate that BRC1 retards all stages of bud development: first, it prevents vegetative AM initiation under long days and AM initiation in cotyledons; second, it delays the progression of bud vegetative development and prevents leaf bud growth and/or expansion; and third, it suppresses lateral shoot elongation. brc mutants were not affected in any other developmental trait, indicating that BRC genes acted exclusively in axillary buds or that their function was redundant in other developmental pathways
  • We have shown that BRC1 acts inside developing buds to promote growth arrest
  • This indicates that BRC1 represents a key point at which signals controlling branching are integrated within axillary buds, allowing plants to tailor their degree of shoot outgrowth to changing conditions
  • The newly found functional conservation of tb1/BRC function between monocots and dicots suggests that the control of axillary bud development, from long-distance signaling to local responses during axillary meristems initiation, bud development, bud dormancy, and branch outgrowth, may be controlled by a conserved set of genetic functions throughout angiosperms that may correspond to an ancestral developmental pathway evolved before the radiation of flowering plants

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