Capsicum annuum homeobox 1 (CaHB1) is a nuclear factor that has roles in plant development, salt tolerance, and pathogen defense.
Homeodomain-leucine zipper (HD-Zip) family proteins are unique to plants, but little is known about their role in defense responses. CaHB1 is a nuclear factor in peppers, belonging to subfamily II of HD-Zip proteins. Here, we determined the role of CaHB1 in the defense response. CaHB1 expression was induced when pepper plants were challenged with Phytophthora capsici, a plant pathogen to which peppers are susceptible, or environmental stresses such as drought and salt stimuli. CaHB1 was also highly expressed in pepper leaves following application of SA, whereas ethephon and MeJA had a moderate effect. To further investigate the function of CaHB1 in plants, we performed gain-of-function study by overexpression of CaHB1 in tomato. CaHB1-transgenic tomatoes showed significant growth enhancement including increased leaf thickness and enlarged cell size (1.8-fold larger than control plants). Microscopic analysis revealed that leaves from CaHB1-transgenic plants had thicker cell walls and cuticle layers than those from controls. Moreover, CaHB1-transgenic plants displayed enhanced resistance against Phytophthora infestans and increased tolerance to salt stress. Additionally, RT-PCR analysis of CaHB1-transgenic tomatoes revealed constitutive up-regulation of multiple genes involved in plant defense and osmotic stress. Therefore, our findings suggest roles for CaHB1 in development, salt stress, and pathogen defense.
Department of Plant Science, College of Agriculture and Life Sciences, Seoul National University, Seou1 151-742, Republic of Korea.
Sang-Keun
SK
Oh
Joonseon
J
Yoon
Gyung Ja
GJ
Choi
Hyun A
HA
Jang
Suk-Yoon
SY
Kwon
Doil
D
Choi
D002212:Capsicum / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D016350:Leucine Zippers; D018551:Solanum lycopersicum / Q000235:genetics / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D055049:Salt Tolerance / Q000235:genetics / Q000502:physiology*; D015854:Up-Regulation
D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins
CaHB1; Homeodomain-leucine zipper; Phytophthora infestans; Plant defense; Salt tolerance