Arabidopsis AtHB7 and AtHB12 evolved divergently to fine tune processes associated with growth and responses to water stress

RÉ DELFINA A.,; CAPELLA, MATIAS; BONAVENTURE GUSTAVO; CHAN RAQUEL

BMC PLANT BIOLOGY

BIOMED CENTRAL LTD

Lugar: Londres; Año: 2014

1471-2229

BackgroundArabidopsis AtHB7 and AtHB12 transcription factors (TFs) belong to the homeodomainleucinezipper subfamily I (HD-Zip I) and present 62% amino acid identity. These TFs havebeen associated with the control of plant development and abiotic stress responses; however,at present it is not completely understood how AtHB7 and AtHB12 regulate these processes.ResultsBy using different expression analysis approaches, we found that AtHB12 is expressed athigher levels during early Arabidopsis thaliana development whereas AtHB7 during laterdevelopmental stages. Moreover, by analysing gene expression in single and doubleArabidopsis mutants and in transgenic plants ectopically expressing these TFs, we discovereda complex mechanism dependent on the plant developmental stage and in which AtHB7 andAtHB12 affect the expression of each other. Phenotypic analysis of transgenic plants revealedthat AtHB12 induces root elongation and leaf development in young plants under standardgrowth conditions, and seed production in water-stressed plants. In contrast, AtHB7 promotesleaf development, chlorophyll levels and photosynthesis and reduces stomatal conductance inmature plants. Moreover AtHB7 delays senescence processes in standard growth conditions.ConclusionsWe demonstrate that AtHB7 and AtHB12 have overlapping yet specific roles in severalprocesses related to development and water stress responses. The analysis of mutant andtransgenic plants indicated that the expression of AtHB7 and AtHB12 is regulated in acoordinated manner, depending on the plant developmental stage and the environmentalconditions. The results suggested that AtHB7 and AtHB12 evolved divergently to fine tuneprocesses associated with development and responses to mild water stress.