Source-to-sink partitioning is altered by changes in the expression of the transcription factor AtHB5 in Arabidopsis

RAMINGER, B LORENA; MIGUEL, VIRGINIA N; ZAPATA, CARLOS; CHAN, RAQUEL L; CABELLO, JULIETA V

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Año: 2023

0022-0957

Carbohydrates are transported from source to sink tissues. The efficiency of such transport determines plant growth and development. The process is finely regulated, and transcription factors are crucial in such modulation. AtHB5 is a homeodomain-leucine zipper I transcription factor, repressed during stem maturation. However, its function in this developmental event was unknown. Here, we investigated the expression pattern and role of AtHB5. AtHB5 localized in conductive tissues: roots, hypocotyls, stems, petioles, pedicels, and central leaf veins. Mutant plants exhibited wider and more lignified stems than controls, whereas overexpressors showed the opposite phenotype. Cross-sections of athb5 mutant stems showed enlarged vascular bundle, xylem, phloem, and petiole areas, whereas AtHB5 overexpressors exhibited callose deposits. Several genes involved in starch biosynthesis and degradation had altered transcript levels in athb5 mutants and AtHB5 overexpressors. Rosette and stem biomasses were enhanced in athb5 mutants, positively impacting seed yield, protein, and lipid content. Moreover, these effects were more evident in debranched plants. Finally, the transport to roots significantly slowed down in AtHB5 overexpressors. Altogether, the results indicated that AtHB5 is a negative modulator of carbon partitioning and sucrose transport from source to sink tissues, and its overexpression diminished plant biomass and seed yield.